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Bleach Is Not Working For Me. Going Back To Dichlor.


TinyBubbles

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Ok, so I'm at the 2 month point with bleach. I have decided to switch back to dichlor. I am tired of fighting the ph battle. My ph stays so high, that I am sick of adding ph down. I knew bleach had a ph of 13, but I didn't think a few ounces a day would make such a big difference. My other problem is trying to maintain a chlorine residual. I simply can not do this with bleach. When I use dichlor, it's still there the next day. I know there are alot of people here that use bleach and I'm curious why they don't report problems with high ph. Do the rest of you have any problem maintaining a chlorine residual? I'm assuming that the high temps. are effecting the bleach. Anyone have any suggestions to change my mind before I make the switch?

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I'm sort of curious why it seems that so many people in this forum are obsessed with keeping a residual in their hot tubs and pools. In my mind, the only reason to bother with keeping a residual is if you operate a public pool of some kind and it's required of you by law. If I'm using a pool or hot tub, I would rather be swimming or soaking in plain clean water, then use the minimum amount of chemicals to disinfect when I get out and have plain clean water again the next day.

Am I crazy? :wacko:

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Your total alkalinity may be too high. I found out that with a starting TA of about 130, which was at the low end of what the tub manufacturer recommended (I added baking soda to get to 130) that pH would be high (about 7.8) every weekend and I would lower it using about 1 - 1.5 tablespoons of "pH Down", only to have it back up there the next weekend. I was using bleach, as well.

In order to determine the TA accurately (and other water parameters), you need a test kit (like the Taylor kit). Those test strips just are not accurate.

Now, about a month into the fill, I think the TA is around 80 - 90, and I no longer have the pH creep and this past weekend, I did not have to add "pH Down" and the pH was right at 7.5. I plan to not add the baking soda at my next fill and the starting TA should be about 80, just right I think.

I could see the manufacturer recommending a higher than 80 TA, since they also say you must use dichlor only. Bleach may necessitate the lower TA, but I will defer to Chem Geek on answering this.

After I filled the tub, I used Dichlor for a couple weeks (CYA was about 45 ppm after 2 weeks) and then switched to 1/3 cup of bleach added BEFORE each soaking in the tub (330 gallons). My wife and I soak once a day on weekdays and twice a day on weekends. I add the bleach before because I like to have chlorine when I soak and I have found there is none, or next to none, if I add it after I soak.

I also weekly shock the tub with 4 tablespoons MPS. I may consider shocking with about a cup of bleach instead of using the MPS. I will check for combined chlorine and if I have too much, I may try the bleach shocking.

--Nate

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Poolyeti, I'm not sure if you are crazy. Do you speak in a Brittish accent like Britney Spears? :) I want to keep a very low residual, but I feel that something should be there. Combine my rapid chlorine loss with the use of bleach and the high ph, and there is not much there to disinfect. I haven't found any information yet that suggests leaving your spa with no residual sanitizer. But, if you are doing it and it's working, then that's good information to have. When I was using dichlor, I could easily keep a slight chlorine residual. Not enough to dry out skin or be irritating. There is no way I would be able to go on vacation and leave the spa unattened while using bleach. I was able to do it successfully with dichlor.

Nate, it's good to know that I'm not the only one with no chlorine residual using bleach. I'm just not willing to add it before I soak, because I do not want to soak when levels are that high. I have kept my TA low, which is why I am so baffled. I had read chemgeeks suggestions on this, before I switched over to bleach. My TA is between 60-80 with a test kit. I really liked the theory of bleach, but right now it's looking better on paper than in reality. Part of me keeps saying that there is a reason that spa manufacturers and dealers recommend dichlor instead of bleach/liquid chlorine. As far as shocking, I've done some research and everything I read suggests that MPS is much more effective at this than chlorine. Just remember, that when shocking with MPS it will show up as cc, unless you have a kit that gives you the option of cancelling it out.

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Ok, so I'm at the 2 month point with bleach. I have decided to switch back to dichlor. I am tired of fighting the ph battle. My ph stays so high, that I am sick of adding ph down. I knew bleach had a ph of 13, but I didn't think a few ounces a day would make such a big difference. My other problem is trying to maintain a chlorine residual. I simply can not do this with bleach. When I use dichlor, it's still there the next day. I know there are alot of people here that use bleach and I'm curious why they don't report problems with high ph. Do the rest of you have any problem maintaining a chlorine residual? I'm assuming that the high temps. are effecting the bleach. Anyone have any suggestions to change my mind before I make the switch?

You are having the problems that I had asked about when I first read the bleach recipe a couple of weeks ago. I am glad to know that my "simplistic" water chemistry knowledge seems to be correct. I would not try to change your mind, the scale that can form at high ph levels just attacts your heater element in spas and jams the heck out of jets. Good luck in your decision

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Rather than completely switch back to Dichlor, why not just raise up to a somewhat higher CYA level by using Dichlor for another week to get to around 40-50 ppm CYA (and if that helps a little and you want even more improvement, then add another week's worth of Dichlor)? That will lower the disinfecting chlorine concentration so should lower its rate of outgassing if that is part of its loss and might lower the rate it reacts with ozone if that is part of its loss. As for the scaling concern that Hillbilly Hot Tub brings up, that won't happen unless you've got higher calcium hardness (CH) in the water and a higher total alkalinity (TA) since scale comes from the combination of calcium and carbonate. A higher pH alone will not cause scale unless it's very high, but at a TA of 70, CH of 150, temp of 104F, the water is saturated with calcium carbonate at a pH of 7.8 -- at a CH of 100, it's saturated at 7.95 so you do want to keep your CH at 100 or below if the pH tends to run high. I suspect that those that keep the TA higher per spa mfg. recommendations would find more scaling as a TA of 120 with CH of 100 would be saturated at a pH of 7.7. Finally, how high is the pH you are talking about? You can readily target a pH of 7.7 instead of 7.5 since the rate of carbon dioxide outgassing (and pH rise) is faster at lower pH and higher TA (assuming you've got a low enough CH as just described to prevent scaling). This link to The Pool Calculator can be used to calculate the Calcite Saturation Index if you input pH, TA, CYA, CH, Temp (you can leave salt as 0 since it will calculate the minimum TDS based on other parameters). Since the heater is at higher temp (around 30F higher at the surface), you can target a CSI of -0.2 though scaling really doesn't occur very much until somewhat positive CSI numbers. A pH of 7.7, TA of 70, CYA of 40, CH of 100, Temp of 104F gives a CSI of around -0.2

This link gives an example in a pool where a TA of 70-100 had some pH rise that had to be dealt with each week. When this person let their TA drop to 40, they found that the pH became stable which is counterintuitive. There have been many similar situations, though not as extreme -- mostly people with TA that was high over 100, including many with SWG pools, and lowering the TA helped lower the pH rise. It's not a huge effect as is seen in this chart which gives the relative rate of carbon dioxide outgassing as a function of pH and TA while this chart shows the relative pH rise since lower TA buffers pH less -- however, most people find more of a relative "pH rise" difference than shown in this second chart (note that the numbers in the chart are relative, not absolute -- so a number that is double another would have twice the rate of pH rise).

As for why you have more of a pH rise issue than others, I suspect it's due to having an ozonator and possibly running it longer than some others and also may be that you have a longer time with the jets running. The ozonator generates oxygen bubbles (plus some ozone) so is aerating the water when it is on. Same with the jets. Both of these processes drive carbon dioxide out of the water and make the pH rise (TA is mostly a measure of carbon dioxide compounds in the water, mostly as bicarbonate). And as you point out, the higher water temp makes the outgassing of chlorine itself more likely and that also causes the pH to rise. However, there is absolutely no difference in the chlorine between the bleach and Dichlor once it is in the water. The use of Dichlor is not pH neutral but actually drops the pH IF there were no outgassing of carbon dioxide. That is, if you used Dichlor in water with very low TA and no jets and no ozonator, the pH would drop over time (assuming that the chlorine got used up, say by oxidizing ammonia/urea) whereas with bleach the pH would remain stable (this is the case in my pool, for example, where I only use chlorinating liquid and keep it covered most of the time and don't have an SWG or any aeration features such as waterfalls, spillovers, fountains). The pH rise you are seeing isn't one factor, but a combination of two (for bleach, pH neutral from chlorine usage plus pH rise from outgassing = net pH rise; for Dichlor, pH drop from chlorine usage plus pH rise from outgassing = net pH neutral; if you used no chlorine at all then you'd still have pH rise from outgassing).

You can, of course, do whatever you want, but if you want to simulate the pH lowering effect of Dichlor, then you could just add bleach and acid (separately, of course) for the same effect but without increasing the CYA level. Over a longer time, you may need to add some baking soda if the TA gets too low, say below 50. I would suggest just adding more Dichlor to get the CYA higher and see if that makes any difference. With your ozonator, the lower disinfection rate from chlorine (due to higher CYA) is not a big issue and remember that my 20 ppm CYA recommendation was conservative anyway. Think of it this way -- which is better: adding Dichlor that continually increases CYA and which decreases disinfecting chlorine or adding both bleach and acid which keeps the CYA constant? Anyway, if you decide to add some more Dichlor and then switch to bleach at a higher CYA level, let us know if that helps at all. Note that Nat is at a higher CYA level of around 45 ppm so that may be helping his situation relative to yours if yours is closer to 20 ppm. The higher CYA level should also have your chlorine last longer when on vacation since the lower disinfecting chlorine concentration slows down all chemical reactions and outgassing of chlorine. The trick will be to find that balance of CYA level that is high enough that might reduce the pH rise and will likely reduce the rate of chlorine usage issues you have but not be so high as to make the disinfection and oxidation rates of chlorine too low. With your ozonator, the latter issues are less of a concern (but not of no concern). Even before your post I was considering raising the recommendation of CYA level for those with ozonators to at least the 40-50 ppm range so your results will be helpful to others as well.

Richard

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Hi Richard. I shared your thoughts about the cya level, so I have previously raised mine all the way to 80, but it hasn't helped. The bleach still won't stay around. I think I mentioned earlier that I went away for 5 days with dichlor and came home to a residual, but I can't maintain one for even half a day with bleach. I've done some digging on the net and discovered that bleach is very unstable and by the time we get it off the shelf, it's already lost part of it's potency. Combine this with constantly opening the container for daily use and it's potency is being further weakened. I read that you have to increase your dosage over time to counteract this effect, but that's too much trouble for me. Maybe that's why it's used more in pools, entire gallons are poured in at once. Also, liquid chlorine, sold in pool supply stores, is more concentrated than household bleach which starts out at only 6% available chlorine, opposed to 62% available chlorine from dichlor. I read that heat causes bleach to decompose, especially when you reach temps of 104, which is common in spa use. Additionally, I read that copper, nickel and other metals rapidly degrade sodium hypochlorite (bleach). I use N2 in my spa, so this could be a contributing factor. I'm considering now, that N2 and bleach might be incompatible. It seems like a stable form of chlorine is much more important in a spa than a pool, which makes sense due to higher temps, higher aeration and a larger demand on the sanitizer. In regards to the ph, I never had a problem keeping the ph locked in when using dichlor. I read that bleach becomes very unstable when mixed with acids, so adding products to the spa to lower the ph sounds counter-productive. I don't want to leave the ph high, because everything I read says that chlorine is very ineffective as a sanitizer at high ph levels. Everything I can find says that ozone will not effect water's ph. I found articles stating that because bleach contains caustic soda, it will raise the ph level when added to water. So, I'm down to this.....bleach is clearly an effective sanitizer, but I don't think it's the best alternative for spas. I definately wanted to try bleach, it's inexpensive and sounded fairly simple. In the long run, it seems it's actually more work for me to maintain my water with it's use. It seems like spas need a stabilized form of chlorine, but it's a catch 22 because that stabilizer can decrease it's effectiveness. While we may not lose our chlorine to the sun like pools, we are losing it to many other factors. That being said, I know there are people here using bleach. I'm curious what is the longest length of time someone has been running their spa with bleach and do they use a mineral cartridge?

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I, too, would be interested in hearing the differences in other's situations since some have a better experience with bleach so it would be good to know why -- are they using Nature2 or other mineral systems and are they using an ozonator?

As you know, I'm only trying to figure all of this out technically along with your experience and the experience of others. I'm not trying to prove any point here. So I will let you know what I know and my thoughts on what you are seeing to see if caveats of usage are needed, as you suggest. Clearly, the bleach works for some people so this isn't as simple as saying only Dichlor should be used. So let's see if we can figure this out and maybe do some tests as you switch back to Dichlor. I'm sorry it didn't work for you, but we can all learn from the experience and adjust the recommendations and maybe even come up with something that might work better for you (i.e. preventing the CYA from continuing to climb).

When the bleach gets mixed in the water, the hypochlorite ion forms some hypochlorous acid and at pH 7.5 they are about equal. This happens very, very quickly. Then the hypochlorous acid runs into some CYA in the water and binds to it. This takes a little longer, but is still within seconds. After a minute or so of mixing (since spa water mixes pretty quickly with the pump running), 97% of the chlorine is attached to CYA, 1.5% is hypochlorite ion, and 1.5% is hypochlorous acid.

With Dichlor, you start out with chlorine bound to CYA and when it gets into water a small portion of it produces hypochlorous acid and then this forms hypochlorite ion. The end result is identical to that from using bleach, assuming the CYA level is the same in both cases. 97% of the chlorine is attached to CYA, 1.5% is hypochlorite ion, and 1.5% is hypochlorous acid.

So if it takes more bleach than Dichlor, based on what is expected, then this either means that the bleach is weaker than you think it is -- i.e. it's not 6% -- or it is getting outgassed or broken down or combining with something else before it's able to combine with the CYA in the water. This should be fairly easy to determine if you measure the FC soon (say 5 minutes) after you've added the bleach. The same test can be done after adding some amount of Dichlor. Then the water can be measured the next day after each situation. That is, if one alternated adding Dichlor one day, seeing the immediate and next day FC, and compared that to adding bleach one day, seeing the immediate and next day FC, then that would be a meaningful comparison. If the FC is lower than expected soon after adding the bleach, then the bleach is either weak or something about how it gets added prevents it from stabilizing quickly enough.

If the bleach was on the weak side so that you weren't adding as much as you thought of chlorine, then you could build up ammonia/urea so that any addition of either bleach or Dichlor at that point would look like it is getting used up very quickly. So see what happens when you switch to Dichlor right away -- if the demand is still high and the Dichlor gets used up before the next day, then this may be what happened. What would be surprising if this happens is why the ozone didn't break down the ammonia/urea.

As for loss in potency of bleach, it depends on the quality of bleach, and the same is true for chlorinating liquid. This link shows the half-life of chlorinating liquid or bleach at various temperatures and concentrations. There is no question that if the bleach is made poorly containing metal contaminants, then it will break down faster in its bottle, but this is still at relatively high concentrations. I use 12.5% chlorinating liquid for my pool and don't find its initial concentration nor its later concentration after a couple of weeks (for one jug; 2 months for 4 jugs) to change in any measurable way and I only add about 4 cups at a time (about every 3-4 days) out of a one gallon jug and I have 4 such jugs at a time (so lasts around 2 months). Of course, it's probably a quality product which may not be true of all bleaches though I'd expect a name brand like Clorox to do a better job (I've measured an old bottle of Clorox in our laundry room and it still measured very close to 6%). I know that off-brand Regular bleaches are 3% or less in concentration and only the Ultra off-brands are "supposed" to be 6% though they do not say so on the bottle (only Clorox says 6% Sodium hypochlorite and also says 5.7% Available Chlorine).

So as far as the Nature2 metal, which is silver, and other metals that catalyze bleach decomposition (iron, nickel, copper), this is all fine and dandy, but would only apply to concentrated solutions since it is just accelerating auto-degradation that only happens with any reasonable speed in such solutions. So maybe if the bleach is added to the spa water, that in the few seconds it is still somewhat concentrated and only mixed with a smaller portion of the water, then the Nature2 metal ions catalyze some breakdown of it. This won't happen as fast with Dichlor because it's not reactive and it's chlorine releases in smaller amounts as it gets mixed. If this is what is happening, then you should be able to measure the chlorine level shortly after adding bleach, say 5 minutes after, and see that the FC is lower than expected and that this does not happen if you repeat this experiment (the next day) with Dichlor. This would be useful information to know. To distinguish between metal ion catalyzed degradation of the bleach vs. a too weak bleach, you'd have to repeat the experiment adding bleach to filtered water (tap water may contain monochloramine) to determine its strength.

As for bleach being unstable with acids, that is true, and dangerous, when mixed together in concentrated form (it produces chlorine gas), but we are talking about having those mixed in diluted chlorinated water, not concentrated form. It is possible that adding the acid to lower the pH accelerates locally some outgassing of chlorine so perhaps more frequent acid addition adds to the effect of auto-breakdown of chlorine. Though the use of chlorine from Dichlor is acidic, it happens slowly and diluted while adding acid is very concentrated so may accelerate the breakdown chlorine locally. At least this would make some sense for what you are seeing. It should be easy to determine if the acid is speeding up chlorine degradation by measuring the FC before and soon after the acid addition.

It is true that bleach and chlorinating liquid contain a small amount of leftover caustic soda (lye; sodium hydroxide), but the amount isn't large enough to have a measurable effect on pH. If it did, then other pool and spa users that use bleach or chlorinating liquid would have their pH rise and most don't if their TA is lower and they don't have as many sources of aeration (SWG, ozonator, jets, waterfalls, spillovers, fountains). Now it's certainly possible that the particular bleach you are using might have more excess lye in it, but I know that both the chlorinating liquid I use and Clorox Regular in our area do not have enough to be measurable. The pH is high, but the usage of chlorine is acidic and compensates for it with virtually no net change in pH over time.

As for chlorine being less effective at higher pH, this isn't as much of an issue when CYA is present -- the effect of pH on chlorine is much less as when CYA is not present. A comparison of the graphs without and with CYA is shown here. With no CYA in the water, the disinfecting chlorine (hypochlorous acid) concentration at 4 ppm FC goes from 3.0 at pH 7.0 to 1.9 at pH 7.5 to 0.9 at pH 8.0. With 20 ppm CYA in the water, the same 4 ppm FC goes from 0.13 at pH 7.0 to 0.10 at pH 7.5 to 0.08 at pH 8.0. So the difference without CYA from a pH of 7.5 to 8.0 is a reduction of 53% while with 20 ppm CYA it is a reduction of 15%. The reason is that CYA acts as a chlorine (specifically, hypochlorous acid) buffer.

So it will be interesting to see what factor seems to cause persistent pH rise even at lower TA when using bleach (my guess is that it's using a strong ozonator that aerates a lot more than jets alone so requires some source of acid to compensate and the use of Dichlor is acidic while the use of bleach is not) and what causes the bleach to not last as long (multiple possibilities here; the strength soon after addition is key).

Richard

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I refilled my tub the day after Christmas, used Dichlor for a couple weeks and bleach ever since. Also have the Nature 2 mineral, and ozone in my D1 Nautilus. I'm of the opinion that maybe a steady (24 hour) amount of FC isn't necessary as long as I stick to my regimen of a daily chlorine addition.

I haven't tested for awhile. The tub's been getting minimal use during our sub-zero temps we've been having for the last couple weeks. I've used it about twice a week. Tonight's test strip showed the pH a bit high, and get this: at 9pm tonight I had about 4 or 5 ppm of FC. This is odd for me, because I add bleach at around 7am each morning. Usually, in a matter of hours, I have no residual. But tonight, it's there. Interesting. I can smell chlorine on my skin, which, if I had my choice, i would prefer to soak in water that doesn't have a "chlorine bite". I haven't worried too much about not having residual. I figure that a daily addition of chlorine is going to kill stuff that needs to be killed. What I have changed lately is that I now add a couple ounces of mps after each soak. I used to just add some more chlorine. Maybe this is resulting in better residual chlorine?

I'll definitely have to keep a closer eye on my pH. Once I got it down using chemgeek's method, I haven't watched it very close, so I really don't know if it's been creeping up significantly.

I definitely have clean, clear water...no problems I had during my first fill. Those problems might have been to newbie mistakes. On the next fill I might use dichlor exclusively just to see if there's any difference. I would still do a daily addition, though, as I think that a lot of my previous problems were due to the bad advice of my dealer, which was shock once a week and add 1 tbsp of dichlor after each soak. Using that method, there were times where no sanitizer was added for days. Not good.

So, I guess my point in all this is this: if you have to do a daily addition, does it really make any difference if you use bleach or dichlor? There's going to be some sanitizing taking place each day (I guess maybe a diminishing effectiveness with dichlor as CYA levels rise, but some sanitizing nonetheless).

David

Hi Richard. I shared your thoughts about the cya level, so I have previously raised mine all the way to 80, but it hasn't helped. The bleach still won't stay around. I think I mentioned earlier that I went away for 5 days with dichlor and came home to a residual, but I can't maintain one for even half a day with bleach. I've done some digging on the net and discovered that bleach is very unstable and by the time we get it off the shelf, it's already lost part of it's potency. Combine this with constantly opening the container for daily use and it's potency is being further weakened. I read that you have to increase your dosage over time to counteract this effect, but that's too much trouble for me. Maybe that's why it's used more in pools, entire gallons are poured in at once. Also, liquid chlorine, sold in pool supply stores, is more concentrated than household bleach which starts out at only 6% available chlorine, opposed to 62% available chlorine from dichlor. I read that heat causes bleach to decompose, especially when you reach temps of 104, which is common in spa use. Additionally, I read that copper, nickel and other metals rapidly degrade sodium hypochlorite (bleach). I use N2 in my spa, so this could be a contributing factor. I'm considering now, that N2 and bleach might be incompatible. It seems like a stable form of chlorine is much more important in a spa than a pool, which makes sense due to higher temps, higher aeration and a larger demand on the sanitizer. In regards to the ph, I never had a problem keeping the ph locked in when using dichlor. I read that bleach becomes very unstable when mixed with acids, so adding products to the spa to lower the ph sounds counter-productive. I don't want to leave the ph high, because everything I read says that chlorine is very ineffective as a sanitizer at high ph levels. Everything I can find says that ozone will not effect water's ph. I found articles stating that because bleach contains caustic soda, it will raise the ph level when added to water. So, I'm down to this.....bleach is clearly an effective sanitizer, but I don't think it's the best alternative for spas. I definately wanted to try bleach, it's inexpensive and sounded fairly simple. In the long run, it seems it's actually more work for me to maintain my water with it's use. It seems like spas need a stabilized form of chlorine, but it's a catch 22 because that stabilizer can decrease it's effectiveness. While we may not lose our chlorine to the sun like pools, we are losing it to many other factors. That being said, I know there are people here using bleach. I'm curious what is the longest length of time someone has been running their spa with bleach and do they use a mineral cartridge?
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I've described my routine once before, but it's very much on topic here as well. I have a 500 gallon spa with a 3-stage filter consisting of a pleated macro filter, a depth filter insert and a mineral cartridge. I do not have ozone at this time. As a general rule, I am using SpaBoss chemicals except for the chlorinating liquid which is HASA 12.5% in the re-fillable bottles and is produced in a nearby town. I initially filled my spa using 4 oz of Stain and Scale preventer. I started on di-chlor for the 1st few weeks , occaisionally suplemented by MPS. The routine I have settled into is that I add 1/2 tblspn MPS for each bather immediately AFTER soakiing in the evening. I leave the cover open and air jets on for about 15 minutes before closing the cover. In the morning, I add about 1/4 cup of chlorinating liquid and run pumps without air for about 15 minutes. I test in the afternoon when I get home from work using FAS-DPD from my TF100 style kit (PS-234.) I usually read about 4-6 ppm chlorine and my CYA is aboout 40 PPM. My alkalinity is fairly low, and I use 1/2 tblspn of dry acid if it's drifting up above 7.5 and a tablespoon of baking soda if it's much below 7.5. About 1/2 hour before I plan to soak, I open the tub and run the pumps with the air jets open to drive out any volitile by-procucts. So far after a little more than 2 months, My water has always been perfectly clear.

Chris W

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Richard, trust me, I don't think you have any kind of agenda or are trying to push anything. In fact, if I did, I wouldn't weigh in with my experience. I figured you would be interested in my information. I don't have an agenda either, other than an EASY water care program. It's interesting to hear David's experience and it's comforting. I'm not the only one that rapidly loses my FC residual when using bleach. As far as Chris' experience, I tend to think the MPS added after soaking to oxidize everything is the reason he maintains a FC residual after adding 12% sodium hypochlorite the next morning. What do you think? I'm just not willing to add things twice a day, but it sounds like it works. David's post brings up a whole different issue.....do you need a FC residual in a spa? I originally assumed that you did not, but after reading this forum the majority of people feel that you do. Also, I had my water get very cloudy and smelly about a week ago and figured it's because of running the spa with no residual. I will try to do some testing with dichlor and bleach over the weekends. I have a long commute and it's just too much for me to do during the work week. I know in the past I've tested about 15 minutes after adding the bleach and I had a sufficient FC reading. I believe it's always been maintaining it's that's the issue. I did get to a point where adding the same amount of bleach did not result in the same FC level so I bought a new bottle of bleach to see if this would make a difference. It did for awhile and then the levels fell off again. That's when I put in the amount of dichlor I used to use and I had a FC residual of 2 24 hours later. Richard, could it be that bleach is a great sanitizer but it's rapidly used up oxidizing in a spa?

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I have had my spa since September and am now on the second fill. It wasn't until a few weeks ago I discovered that the only way I could maintain good quality water with chlorine and an ozonator was to add a daily dose of MPS. I prefer to have as little chlorine as possible, but still above zero, in the tub when I get in.

I went through a few weeks trying to get chlorine to last more than a few hours (like >12PPM to 0 in 4-6 hours) with bleach, dichlor and lithium and found no difference between the different types even with the ozonator off. I was ready to take an axe to the stupid thing.

I have a cupboard full of products: dichlor, lithium, clarifier, de-foamer, stain-away, ph-down, MPS and of course bleach. The only thing I use now is MPS and bleach and the water maintains that same 'crispness' as when it was fresh. Worked, for me, YMMV, etc, but I am amazed at how simple the solution turned out to be in my situation.

The TA is around 100, CYA around 20. The pH tends to go down if the spa gets only intermittent use (does not happen very often) but goes back up after use.

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OK, some patterns are emerging here.

Chlorine goes away

Nat's situation is more what is expected where adding either Dichlor or bleach resulted in very little chlorine the next day. The solution is to use more, assuming one wants to keep some residual at all times and that is the safest thing to do (I talk more about that below). I'll also talk about MPS later. Nat wrote in another post about using a no-name brand for bleach at one point and it required using twice as much to get the expected chlorine amount. Regardless of whether the chlorine residual disappears because the initial addition is using bleach that is too weak or whether it dissipates faster for some reason, the solution is to use more chlorine either adding more frequently or adding more to get to a higher FC level. If a higher FC level is used, then a higher CYA level would make more sense so that the disinfecting chlorine level is somewhat consistent. If the CYA is at 50 ppm, then there is nothing wrong at all with a 10 ppm FC; the CYA just acts as a chlorine buffer holding more chlorine "in storage" to handle larger bather loads.

I think there is this fear as to the quantity of chlorine needed to oxidize the ammonia/urea from sweat, but as some rough calculations showed in this post, one person-hour of soaking in 350 gallons can use 7 ppm FC (2.3 ppm FC for 20 minutes) and this doesn't count the normal loss that occurs when the tub is not used. This is not a hard and fast rule as the amount people sweat varies, but it does roughly correlate with what most people have been seeing. The 3-4 ppm FC per day I've generally been saying would probably only apply to shorter soaks (20-30 minutes) of one person.

Once you get behind in oxidizing the ammonia/urea from sweat, it just sits in the spa (assuming no MPS or ozonator is used to oxidize it) and builds up making it seem that the added chlorine gets used up almost immediately and never seems enough. Only a large shock with chlorine or MPS would rid the spa of this ammonia/urea. Fortunately, it is very easy to tell if this situation is occurring if you have a good test kit. If you add chlorine and you measure (within a few minutes) FC with no (< 0.5 ppm) CC, then you've oxidized all the ammonia/urea. If you measure CC, then you've most likely got monochloramine which is chlorine combined with ammonia/urea (this happens if you add chlorine after a soak and didn't have much chlorine when you got in). If you are adding enough chlorine, then this CC will go away over hours and you will still have some FC leftover with no CC. If you don't have any FC leftover, then you aren't using enough chlorine. So if you test before you get into the spa, then you know you've been doing things right if you measure some FC (say, at least 0.5 ppm FC or 1 ppm FC) with no (< 0.5 ppm) CC. If you measure CC, then you aren't using enough chlorine or you have too much CYA in the water. If there's too much CYA, then the breakpoint doesn't happen fast enough so buildup can occur that way, even if you use enough "capacity" of chlorine.

Chlorine residual

As for whether to add the chlorine before the soak or after the soak, there are pros and cons each way. If you do so before the soak, then you significantly reduce the risk of transmission of any pathogens from person to person (mostly fecal to oral route), but this risk is already very small in a personal spa or pool. It's much more important in a commercial or public situation where one sick person can infect dozens. The main downside to adding the chlorine before the soak is that it will combine with your sweat to produce chloramine and that can smell -- the chloramine will break down but this takes time (it's fast to form, even at high CYA levels, but it's slow to break down, slower at higher CYA levels). There is nothing wrong with it as the concentrations are relatively low, but it's obviously a personal choice since it can smell. Chlorine exposure also dries/flakes skin and frizzes hair, but this is less of a problem with some CYA in the water (so is more of a problem in indoor pools where CYA is typically not used).

In terms of importance, having a chlorine residual, even a small one (0.5 ppm) at nearly all times is what is most important. With no chlorine in the water at all, bacteria can start multiplying and they do so quickly (doubling in 15 minutes to an hour in good conditions). In practice, if you add chlorine every day and only have no residual for a couple of hours each day, then the risk is low, but you should really shoot for having some chlorine residual at all times since underestimating wouldn't be good. As for using only Dichlor, the buildup of CYA makes the chlorine less effective, but most bacteria are very easy to kill. We still do not know for sure what the real story is with the bacteria that causes hot tub itch (the sources vary and results on this forum are not conclusive). Nevertheless, the slower breakpoint problems from the higher CYA are also annoying, but of course one can just replace their water when things start to go south (or before then, if one gets a sense for how often that is).

Non-chlorine shock (MPS)

As David, Chris, lmartine and others in other threads have reported, using MPS usually results in a lessening of chlorine demand. This makes perfect sense since it oxidizes ammonia/urea and other organics just like chlorine does and usually does so faster so if both are present in the water, the MPS will take precedence. The question becomes whether it's actually necessary to use MPS or not. I would say it's not necessary (at least not daily), but if you don't then you may have to use what seems to be large amounts of chlorine. So MPS as a daily supplement does have some advantages. If you add it before you soak, then it will combine with any sweat and not produce any chloramines or other disinfection byproducts. The problem is that it is irritating and you'd need to add it at least 20 minutes before getting into the spa to minimize that (but some are sensitive to it anyway). If you add it after you soak, then you can avoid some of the irritation problems unless you are particularly sensitive (and depending on how much you add), but may still get some chloramines with whatever chlorine is left in the water when you start your soak. You've heard different timings of MPS and chlorine addition. The main thing to get lower chlorine usage is to make sure you add MPS before you add chlorine, not the other way around. Give the MPS a chance to oxidize ammonia/urea and organics and then chlorine can be added for sanitation in potentially smaller amounts that still stick around for a while.

I would say that if one wants to soak in a minimally chemical environment (ignoring the low person-to-person transmission risk), then using MPS after a soak, then waiting about a half hour, then adding chlorine so that a very small residual (perhaps 0.5 ppm) is present when you get in for the next soak would be ideal, but no one has tried that so it might not work. The closest to this is the MPS after soak and chlorine in the morning that Chris does. lmartine, when do you add your MPS and chlorine?

pH rise

It seems that not having an ozonator and lowering the TA reduces the pH rise problem as Nat has found. The other approach is to use acid in some form such as using Dichlor or MPS or dry acid. All of these are acidic (the Dichlor is net acidic when the chlorine gets used up). So if one has an ozonator or one has particularly vigorous aeration from jets, then it just may not be worth trying to fight the rising pH (even at lower TA) when using a hypochlorite source of chlorine (such as bleach) alone. Using Dichlor results in an increase in CYA over time with its side effects I've already discussed. Using MPS as described above therefore seems to be a very reasonable balanced solution since using both MPS and bleach (after initial Dichlor to get CYA to a reasonable level) results in using less bleach and the MPS is acidic so performs some of that function that Dichlor would have done.

As for specifics, here's some equivalents. 1 tablespoon of MPS is equivalent to 2 fluid ounces of 6% bleach (about 3 ppm FC in 350 gallons). If we assume that one person-hour of soaking indeed requires the equivalent of 7 ppm FC in 350 gallons, then this would be 5 fluid ounces of 6% bleach or 7 teaspoons (2-1/2 tablespoons) of MPS or some balanced combination of each per person-hour of spa use and these amounts are independent of spa volume. As far as the acidity of Dichlor vs. MPS is concerned, the 5 fluid ounces of 6% bleach is equivalent to 3-1/2 teaspoons of Dichlor (dihydrate). This amount of Dichlor is equivalent in acidity (after the chlorine gets used up) to 1-3/4 teaspoons of Dry Acid. The 7 teaspoons of slightly buffered (43% MPS with 2% magnesium carbonate) MPS is equivalent to 0.6 teaspoons (a little more than 1/2 teaspoon) of Dry Acid. Using buffered MPS (<< 43%) wouldn't be acidic. So for equivalent amounts of oxidation, the Dichlor is almost three times as acidic as MPS. So while using MPS and bleach will be better at fighting rising pH than using bleach alone, it won't fight it as much as using Dichlor. So having the TA lower is probably also needed and there's no guarantee even that will be enough to prevent supplemental use of Dry Acid, but at least it's something to try.

Chris' routine with 1/4 cup (2 fluid ounces) of 12.5% chlorinating liquid in 500 gallons is 3.9 ppm FC. The 1/2 tablespoon of MPS for each bather after soaking is about equivalent to 1 ppm FC per person so not very much. Chris, if you have more specifics with regards to soak time and the number of people soaking, that would be helpful.

The bottom line is that supplementing with daily MPS will reduce chlorine usage and may help the pH rise problem most associated with use of an ozonator (along with keeping the lower TA level).

Richard

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I add the bleach and MPS at the same time, dumping the bleach directly from a measuring cup (no premix) into the tub over a large output jet, pump on high with no air, rinse the cup and then immediately throw the dry MPS on the top.

I realize it would be better add the bleach and MPS at different times, but I want to minimize the maintenance trips out to the spa. I prefer a regular maintenance schedule in the off-hours rather then adding stuff just before or just after use. I'm sure this approach has left me with zero disinfectant at times, depending on the bather load, but I think the ozonator has saved my bacon here.

Lee

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I've said it before and I will say it again...chlorine in a spa requires daily testing and maintenance. It is certainly more work than chlorine in a pool because of the small volume of water to bather load and the higher temps. This is the one thing that makes bromine more attractive (However I personally will never go back to bromine!)

The reason for a FAST ACTING (leaves out metals!) residual sanitizer in the water at all times is to prevent the spread of water borne illness. If you have two or three bathers in the tub each one, no matter how clean, is introducing sweat, uring and feces into the water. Given that some of the enteric water borne illness microbes can reproduce at very fast rates at the higher temps in a tub I hope you see the reason to maintain the residual sanitizer at all times. People freak out about soaking in a tub that has a residual of chlorine but think nothing of swimming in a pool for perhaps 2-3 times as long that has the same chlorine residual!

The residual in either a pool or spa will not last and most likely needs to be replenished daily. People accecpt this with a pool but with a spa it becomes an issue.

In fact, a spa with the proper residual chlorine level before a soak will most probably NOT have one left after! If you find that you need to bump up the FC 1-2 ppm before you soak what is the big deal. You can enter the tub immediately after doing so! Shock after you soak and then you don't have to worry about needing to wait to use the tub!

I suspect that when one is using dichlor and they find that their chlorine residual is lasting that the CYA has probably gone through the roof!

Also, why stress out whether youir bleach is weak or not? Dose the water and then test it! If the FC is low you know you need to add more! Just dosing the water and not retesting after is not good practice. Also, it might not be the strength of the bleach at fault. It might be that you have an inaccurate number for your water volume.

Do you make pH adjustments and not test afterwards?

Do you adjust TA and not test afterwards?

Then why adust sanitizer and not test afterwards!?

pH is GOING to rise in a tub because of all the aeration! It's a fact of life. IF you use acidic MPS and dichlor or bromine tablets then the pH rise is not as apparant but the drop in TA is, which is why the high TA of up to 150 ppm is usually recommened for tubs. It assumes the use of these sanitizes and oxidizers. IF you are using unstabilized chlorine (I don't care if it's bleach, cal hypo, or lithium hypochlorite!) then DROP you TA to about 60-80 ppm and maintain your pH at 7.6 and not lower to slow the outgassing of CO2 and the pH rise it causes. When the pH hits 7.8 is when you want to drop it back down to 7.6. A short while of daily testing and a bit of trial and error and you will soon know that, under normal use, your spa needs to have the pH lowered every X days by adding Y amount of pH decreaser.

Bottom line, your pH WILL rise unless you never use you bubblers and venturi jets (but then why have a spa? :rolleyes: ) Adjusting the pH is not that big a deal once you figure it all out!

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The problem I have with bleach is that no matter how much I added I could not acheive a FC residual in my spa. I dosed it up to 20ppm and a few hours later, nothing. So weak or strong, the bleach will not last. I work full time and have a family, I don't want to test my water every few hours and add bleach. I agree completely that you need a FC residual, I challenge someone to prove that can be achieved with bleach, unless you add it several times a day. I ran my spa for about 6-7 weeks with no FC residual while using bleach and it turned into a cesspool. Before that, I thought it would be ok to zap things after soaking and then leave the water alone until the next day when we soaked. Apparently, things were multiplying in there the whole time. With dichlor, even with a low cya level, it's been easy to maintain a FC residual.

I believe the reason most people don't like soaking in a spa with a high chlorine level is the hot water. It opens up our pores and makes sanitizer more irritating. Obviously, there are many people without skin sensitivities that are ok to add their sanitizer before soaking. I had a problem with MPS so I wasn't using it. From reading posts, it became clear that it's very beneficial. I experimented this weekend, with throwing in a little mps after a soak and a couple minutes later adding dichlor. WOW. When I added the dose of dichlor I usually use to hit the 3-5 ppm FC mark, it went all the way up to atleast 10ppm, maybe higher. Tried the same thing with bleach isntead of dichlor, the bleach still disappeared. Apparently, just a small amount of MPS is a fast and powerful oxidizer. It seems that by the time the dichlor is added, there isn't much for it to do. So far, I haven't had any reaction to the small amount of MPS added 24 before soaking. Now I'm curious about the product that was a mps/dichlor combo that a friend of mine had suggested right after I purchased my spa. Seems like that would make sense.

Oh, as far as PH is concerned. I can't wait to do another refill. With my first fill, using strictly dichlor, my PH never went up. 2nd fill with bleach, it went up and stayed up. I'm assuming next time I fill and use dichlor, my PH will stay low again. We'll see. While adjusting PH might not be rocket science, I have no desire to constantly adjust one more thing in my spa. Plus, it's adding more chemicals to the spa and I'd rather not do that.

I think I've mentioned before, I want the easiest route to healthy water. I tried bleach thinking it could be the answer. It wasn't. I'm back to dichlor.

"The alkalinity of the sodium hypochlorite solution also causes the precipitation of minerals such as calcium carbonate, so that the shock chlorination is often accompanied by a clogging effect. The precipitate also preserves bacteria, making this practice somewhat less effective." I found this quote someone disturbing about the use of bleach to disenfect water, especially in a hot tub where we don't want things building up in the lines, jets or equipment. In addition, I found this quote "Hot water increases the activity of the bleach, owing to the thermal decomposition of hypochlorite which ultimately generates environmentally-undesirable chlorate." If heat decomposes bleach, why am I using is in a hot tub? I found this in another article "What happens to the pH value when sodium hypochlorite is added to water? Due to the presence of caustic soda in sodium hypo chlorite, the pH of the water is increased." And this:"Bleach cannot be combined with acids. When bleach comes in contact with acids the hypochlorite becomes instable". This led me to believe I can't be successful keeping bleach around in spa water with a correct ph. Then there is this quote: "When it is added to water, sodium hypochlorite increases the pH value. It is better to use chlorine as a disinfectant and an oxidizer." I haven't one thing that suggests that bleach and hot tubs are a good match. Clearly, bleach is an effective sanitizer, but that doesn't mean it's suited for this application. Which is probably why nobody markets a liquid chlorine product for use in spas.

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The problem I have with bleach is that no matter how much I added I could not acheive a FC residual in my spa. I dosed it up to 20ppm and a few hours later, nothing. So weak or strong, the bleach will not last. I work full time and have a family, I don't want to test my water every few hours and add bleach. I agree completely that you need a FC residual, I challenge someone to prove that can be achieved with bleach, unless you add it several times a day. I ran my spa for about 6-7 weeks with no FC residual while using bleach and it turned into a cesspool. Before that, I thought it would be ok to zap things after soaking and then leave the water alone until the next day when we soaked. Apparently, things were multiplying in there the whole time. With dichlor, even with a low cya level, it's been easy to maintain a FC residual.

I believe the reason most people don't like soaking in a spa with a high chlorine level is the hot water. It opens up our pores and makes sanitizer more irritating. Obviously, there are many people without skin sensitivities that are ok to add their sanitizer before soaking. I had a problem with MPS so I wasn't using it. From reading posts, it became clear that it's very beneficial. I experimented this weekend, with throwing in a little mps after a soak and a couple minutes later adding dichlor. WOW. When I added the dose of dichlor I usually use to hit the 3-5 ppm FC mark, it went all the way up to atleast 10ppm, maybe higher. Tried the same thing with bleach isntead of dichlor, the bleach still disappeared. Apparently, just a small amount of MPS is a fast and powerful oxidizer. It seems that by the time the dichlor is added, there isn't much for it to do. So far, I haven't had any reaction to the small amount of MPS added 24 before soaking. Now I'm curious about the product that was a mps/dichlor combo that a friend of mine had suggested right after I purchased my spa. Seems like that would make sense.

Oh, as far as PH is concerned. I can't wait to do another refill. With my first fill, using strictly dichlor, my PH never went up. 2nd fill with bleach, it went up and stayed up. I'm assuming next time I fill and use dichlor, my PH will stay low again. We'll see. While adjusting PH might not be rocket science, I have no desire to constantly adjust one more thing in my spa. Plus, it's adding more chemicals to the spa and I'd rather not do that.

I think I've mentioned before, I want the easiest route to healthy water. I tried bleach thinking it could be the answer. It wasn't. I'm back to dichlor.

"The alkalinity of the sodium hypochlorite solution also causes the precipitation of minerals such as calcium carbonate, so that the shock chlorination is often accompanied by a clogging effect. The precipitate also preserves bacteria, making this practice somewhat less effective." I found this quote someone disturbing about the use of bleach to disenfect water, especially in a hot tub where we don't want things building up in the lines, jets or equipment. In addition, I found this quote "Hot water increases the activity of the bleach, owing to the thermal decomposition of hypochlorite which ultimately generates environmentally-undesirable chlorate." If heat decomposes bleach, why am I using is in a hot tub? I found this in another article "What happens to the pH value when sodium hypochlorite is added to water? Due to the presence of caustic soda in sodium hypo chlorite, the pH of the water is increased." And this:"Bleach cannot be combined with acids. When bleach comes in contact with acids the hypochlorite becomes instable". This led me to believe I can't be successful keeping bleach around in spa water with a correct ph. Then there is this quote: "When it is added to water, sodium hypochlorite increases the pH value. It is better to use chlorine as a disinfectant and an oxidizer." I haven't one thing that suggests that bleach and hot tubs are a good match. Clearly, bleach is an effective sanitizer, but that doesn't mean it's suited for this application. Which is probably why nobody markets a liquid chlorine product for use in spas.

Thank You Tiny bubbles, Glad to know as a dealer I am not trying to rip off my customers, just do whats best for their investment and time.

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TinyBubbles,

I want to remind you of what was said initially after you started using bleach in this post. You said that a little went a long way, implying that it didn't take very much bleach and you decreased your dose to 1-1/2 ounces in 350 gallons which would only be about 2 ppm FC and would not normally be enough to keep up with the ammonia/urea from a normal soak. I suspect that it did not immediately react with the ammonia/urea so you initially measured a higher FC than would have really stuck around. If you got behind in oxidizing the ammonia/urea, then it would take even more chlorine the next time to handle it (though I don't know why the ozonator wouldn't have taken care of it). [EDIT] In this post is when you describe how bleach doesn't hold a residual no matter how much you use. In this post above you mention how the water got cloudy and smelly about a week ago possibly because you thought there was no residual, but the ozonator should have been oxidizing organics and keeping the water clear even if chlorine were not present -- I wonder if your ozonator isn't really working and producing ozone (though is producing aeration from injected air). The situation sounds like a buildup of ammonia/urea and other organics not getting oxidized by the ozonator nor the bleach. [END-EDIT]

What brand of bleach were you using? If you added MPS and the Dichlor amount that usually went to 3-5 now went to 10 or more, then that means you had a LOT of ammonia/urea in the water since that is what either MPS would oxidize or chlorine would combine with (to form monochloramine) relatively quickly. In other words, you had a nearly instant demand of 5+ ppm. Also, you apparently were adding a lot more chlorine from Dichlor than you normally added with bleach. [EDIT] OR if the MPS didn't get used up, then it can register as chlorine in the test unless the special deox reagent is used to remove interference (though Chris W below reports that the deox test may not reliably remove interference at higher MPS levels). [END-EDIT]. It just sounds to me like whatever bleach you were using wasn't any good or way too little was being added each day. I don't know if that means it was too weak to begin with or whether it had some contaminants in it, but something is strange about it. As I said before, if you don't add enough MPS or chlorine to oxidize the ammonia/urea, then any additional you add will get very quickly used up and you'll have no residual. It sounds like the amount of Dichlor you add is much, much higher than the amount of bleach. I'm guessing that with an off-brand Regular bleach that it was less than 3% (maybe much less).

Also, does your brand of Dichlor say "dihydrate" or "anhydrous"? All of my calculations for the amount of FC from Dichlor were for the more common dihydrate form.

The only thing that I have no explanation for is when you say you added bleach to initially measure 20 ppm FC (I assume you measured it with the test kit and didn't just add an amount that you thought was 20 ppm FC) and that within a few hours it went to zero. Perhaps it takes a little longer than I thought for the chlorine to combine with ammonia/urea so initially it would measure FC but would soon drop.

The quotes you've written I've already discussed so won't repeat that here. I fully expect your pH to be more stable when using Dichlor as it is more acidic. Over time, the TA will drop from its use. Even if you were to use a better brand of bleach and used a larger quantity to correspond more with the amount of Dichlor you normally use, then you'd still have the pH rising issue (which would require acid to compensate). At least if you use MPS with the Dichlor (and add it first) then you'll add less Dichlor than you normally do so the buildup of CYA will be slower. You mentioned a sensitivity to MPS in other posts, but maybe if you don't add too much and do so after a soak that it will take care of most of the ammonia/urea letting you use less chlorine (and hopefully having the MPS get used up so it doesn't bother you the next day during soaking).

Hillbilly Hot Tub,

No one was accusing you of ripping off your customers (at least I wasn't). The use of bleach works for some, but in this case it didn't. That doesn't change the issue of lower disinfection over time due to CYA buildup, even if one changes the water after 3 months. At least with some MPS usage, the buildup should be slower.

Richard

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I don't have time at the moment to type up a the whole story, but I found some deox reagent locally and spent a good portion of last weekend testing to try and determine how much MPS Is appropriate. Right now I can say that if the goal is to maintain any residual MPS, it takes more than I was using. I usally have one or two people in the tub for about 15 minutes and occaisionally a third person. I'm still trying to sort out the effectiveness of the deox reagent in conjunction with the FAS-DPD test, I think the test may give strange results if there is more than a few PPM of MPS residual.

Tinybubbles said: "Which is probably why nobody markets a liquid chlorine product for use in spas."

I'm not endorsing this prduct or this brand of products, but at least one company does market bleach for Spas. If you look at either the label or the MSDS, this product is clearly a form of bleach:

http://www.kem-tek.com/spakemyellow.html

http://www.kem-tek.com/spapage.htm

Chris W

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TinyBubbles,

I want to remind you of what was said initially after you started using bleach in this post. You said that a little went a long way, implying that it didn't take very much bleach and you decreased your dose to 1-1/2 ounces in 350 gallons which would only be about 2 ppm FC and would not normally be enough to keep up with the ammonia/urea from a normal soak. I suspect that it did not immediately react with the ammonia/urea so you initially measured a higher FC than would have really stuck around. If you got behind in oxidizing the ammonia/urea, then it would take even more chlorine the next time to handle it (though I don't know why the ozonator wouldn't have taken care of it).

What brand of bleach were you using? If you added MPS and the Dichlor amount that usually went to 3-5 now went to 10 or more, then that means you had a LOT of ammonia/urea in the water since that is what either MPS would oxidize or chlorine would combine with (to form monochloramine) relatively quickly. In other words, you had a nearly instant demand of 5+ ppm. Also, you apparently were adding a lot more chlorine from Dichlor than you normally added with bleach. It just sounds to me like whatever bleach you were using wasn't any good or way too little was being added each day. I don't know if that means it was too weak to begin with or whether it had some contaminants in it, but something is strange about it. As I said before, if you don't add enough MPS or chlorine to oxidize the ammonia/urea, then any additional you add will get very quickly used up and you'll have no residual. It sounds like the amount of Dichlor you add is much, much higher than the amount of bleach. I'm guessing that with an off-brand Regular bleach that it was less than 3% (maybe much less).

Also, does your brand of Dichlor say "dihydrate" or "anhydrous"? All of my calculations for the amount of FC from Dichlor were for the more common dihydrate form.

The only thing that I have no explanation for is when you say you added bleach to initially measure 20 ppm FC (I assume you measured it with the test kit and didn't just add an amount that you thought was 20 ppm FC) and that within a few hours it went to zero. Perhaps it takes a little longer than I thought for the chlorine to combine with ammonia/urea so initially it would measure FC but would soon drop.

The quotes you've written I've already discussed so won't repeat that here. I fully expect your pH to be more stable when using Dichlor as it is more acidic. Over time, the TA will drop from its use. Even if you were to use a better brand of bleach and used a larger quantity to correspond more with the amount of Dichlor you normally use, then you'd still have the pH rising issue (which would require acid to compensate). At least if you use MPS with the Dichlor (and add it first) then you'll add less Dichlor than you normally do so the buildup of CYA will be slower. You mentioned a sensitivity to MPS in other posts, but maybe if you don't add too much and do so after a soak that it will take care of most of the ammonia/urea letting you use less chlorine (and hopefully having the MPS get used up so it doesn't bother you the next day during soaking).

Hillbilly Hot Tub,

No one was accusing you of ripping off your customers (at least I wasn't). The use of bleach works for some, but in this case it didn't. That doesn't change the issue of lower disinfection over time due to CYA buildup, even if one changes the water after 3 months. At least with some MPS usage, the buildup should be slower.

Richard

Hi Richard. That post was 13 days into my bleach usage. I was operating under the assumption that I was ok getting the FC reading of 3-5 15 minutes after adding the bleach and that I did not need a residual. I think it was waterbear that posted somewhere about needing a higher residual even with N2 and was in the camp that didn't think it was needed. I changed my mind about needing the residual after my water went south. I have always tested the FC, I've never guessed that I added enough. In fact, I'm an "over-tester" and use test strips and a test kit. No matter which sanitizer I'm using, I've always gone for the 3-5 ppm FC after adding the product. I was bumping it up at the end with bleach once I realized how quickly I was losing my residual. I've always tested 24 hours later and just assumed it had only recently disappeared. I tried dichlor to discover if it was an increased demand, but it wasn't. I really need to refill my tub and start over with dichlor to make more accurate comparisons, but it's just too soon. When you mention a high level or ammonia/urea and chlorine combining with it, wouldn't this show up as CC? I've never had an issue with CC, I've always assumed it was my ozonator doing it's job. As far as the instant demand, why would it use up bleach but not dichlor? I experimented with both and only lost bleach, not dichlor. Like I said, my next refill should help answer alot of questions. At this point, I don't know if high CYA levels from 3 months of using dichlor will cause problems. So far, no sensitivity with adding a little bit of mps 24 hours before soaking. I'm only adding 1/2 tsp at this point. I'm not really interested in a residual of MPS. Originally I wondered if it could boost my bleach somehow. That led me to wonder if it would boost my dichlor. Sometimes I wonder if I wonder too much! :)

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Ammonia/urea won't show up as Combined Chlorine (CC) unless there is some chlorine in the water that combines with it. If there is an excess of ammonia/urea and too little chlorine to oxidize it, then you can have the excess ammonia/urea hang around and not measure as CC but seem as if there is a large demand for chlorine the next time you add some.

You are right that there is no decent explanation for losing bleach and not Dichlor if you measure the FC of both after addition (and they are the same and the spa usage was the same) and then hours later only the bleach declined and not the Dichlor. If there were no CYA in the water, then the difference could be explained by Dichlor adding CYA, but with CYA already in the water, then Dichlor doesn't add enough to explain this difference. What is weird is why this difference is showing up for you so much more than with others -- it's not that they don't use a lot of bleach, but they can end up with a small residual by using more. That's why I asked what brand of bleach you were using since something seems strange about it.

I'm sure that if you go back to your Dichlor routine that it will work better for you because it lasted longer and is acidic so prevents the rise in pH (though will lower TA over time). Perhaps by supplementing with MPS after a soak you can have it oxidize more organics so you can use less Dichlor which would have you build up less CYA over time. As I edited in my post above, something is strange about your ozonator situation since your water gets cloudy if you don't add chlorine to it. Also, you reported in another post that you sometimes measured CC with Dichlor but didn't with bleach, but that may have been due to a buildup of CYA (using Dichlor only) and slower breakpoint, but would also point to a malfunctioning ozonator.

Richard

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I think the CC readings I had originally were due to MPS in the water. At the time, I did not know that they registered as CC. Then I stopped using MPS due to my sensitivity and viola, no CC. So chalk that one up to my ignorance on the subject.

Just as you posted, my hope is that I can supplement dichlor with MPS and keep my CYA levels as low as possible. I guess I'll be the guinea pig and experiment to see what ratio I can get away with. Unfortunately, I could reach a point with the MPS where I break out again. It sounds like Chris is interested in the same thing, so perhaps we can help each other with that. I might pick up zodiac's test strips to make testing for the MPS faster, while I'm trying to sort through this.

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I don't have time at the moment to type up a the whole story, but I found some deox reagent locally and spent a good portion of last weekend testing to try and determine how much MPS Is appropriate. Right now I can say that if the goal is to maintain any residual MPS, it takes more than I was using. I usally have one or two people in the tub for about 15 minutes and occaisionally a third person. I'm still trying to sort out the effectiveness of the deox reagent in conjunction with the FAS-DPD test, I think the test may give strange results if there is more than a few PPM of MPS residual.

Tinybubbles said: "Which is probably why nobody markets a liquid chlorine product for use in spas."

I'm not endorsing this prduct or this brand of products, but at least one company does market bleach for Spas. If you look at either the label or the MSDS, this product is clearly a form of bleach:

http://www.kem-tek.com/spakemyellow.html

http://www.kem-tek.com/spapage.htm

Chris W

Chris, those were very interesting links. They suggest dichlor for sanitizing the spa: SANITIZING: Is a very critical part of keeping your spa/hot tub free from algae and bacterial growth. Due to the importance of keeping your spa clean, sanitizer levels should be tested several times a week to maintain them in the proper range, even when the spa has not been used. Then they suggest sodium hypochlorite (bleach) for shocking: SHOCKING OR SUPER CHLORINATING: With regular spa or hot tub use there will be an increased amount of non-filterable wastes such as perspiration, oils and organic material that can accumulate. To prevent organic waste or cloudy water build-up, you should shock treat your spa every 7 to 10 days depending on the level of use. This will oxidize and remove waste materials before they become a problem. It is also a good idea to shock your spa after a large number of people use it or, if it is an outdoor spa, after a heavy rain.

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I read a large part of this but there is a lot of text.. Just to give you my bleach experience. Bleach works great for me. No problems. I to experienced the rising PH "problem" that tiny is having. I also was constantly aerating my water. Didn't know you could turn that off, : ). After turning off aeration and using 3/4 of a bottle of PH down dry acid my PH is stable. It isn't rising with use of bleach. There is another reason your PH is rising. As far as residual goes I have very good luck maintaining a residual if the tub isn't being used. No hard numbers but I don't have to add sanitizer every day or every other day if I'm not using it.

I'm dosing my tub with MPS to remove the combined chlorines. From what I understand they might leave on their own with normal bleach use? Or do you have to shock them with bleach if you are not using MPS? Basicaly I test. Adjust PH. Add MPS tsp/1ppm/350 gal of water CC. Adjust my free chlorine. Smooth sailing.

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I read a large part of this but there is a lot of text.. Just to give you my bleach experience. Bleach works great for me. No problems. I to experienced the rising PH "problem" that tiny is having. I also was constantly aerating my water. Didn't know you could turn that off, : ). After turning off aeration and using 3/4 of a bottle of PH down dry acid my PH is stable. It isn't rising with use of bleach. There is another reason your PH is rising. As far as residual goes I have very good luck maintaining a residual if the tub isn't being used. No hard numbers but I don't have to add sanitizer every day or every other day if I'm not using it.

I'm dosing my tub with MPS to remove the combined chlorines. From what I understand they might leave on their own with normal bleach use? Or do you have to shock them with bleach if you are not using MPS? Basicaly I test. Adjust PH. Add MPS tsp/1ppm/350 gal of water CC. Adjust my free chlorine. Smooth sailing.

Well, I must admit, I never put in such a large quantity of ph down. Maybe that is what it takes. I'm concerned with adding so much and raising my TDS. When you say you turned your aeration off, what do you mean? Did you turn it off while you were adjusting your ph or you can never use it now? How often are you dosing with MPS? What level do you get your FC to in order to retain a residual? I don't think your CC will go away unless you shock with MPS or some source of chlorine or run an ozonator. Some people have mentioned that exposing their water to sunlight has broken them down. If you've achieved smooth sailing you are in a good place. I could probably be in smooth water if I'd quit experimenting. I think after my current testing with MPS I'll just stick to a routine. Thanks for your input.

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