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Guadian (SWT) vs SpaBalancer vs Chlorine treatment


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Cool, keep me posted! I recognize the fear of using chlorine, it's the main reason we used a non-chlorine sanitizer in the first place. I have never used of read much about bromine, but read positive things about that too. I am curious how switching to chlorine turns out for you / your wife. After doing all these research (and after all your help) I am convinced that the dichlor/bleach approach is the way to go (for me at least) and will hopefully give me a clear tub for a longer time. 

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HI MPurcell,

I am about to change my water and I am working out a couple things on paper as preparation.

Reading the dichlor/bleach method again I was wondering one thing about the amount of dichlor I would have to add after soaks. It says: "Approx 7ppm FC per person per hour". But using the poolcalculator I did some math. If I soak for 2 hours with 4 persons in a 330 gallon tub, at 37 degrees celcius (98.6 degrees fahrenheit), this would mean I have to add 4*2*7ppm FC. This means I would have to add something like 125gram of dichlor granule. That doesn't seem right. Did I misunderstand something? Because creating that high FC level in the spa, isn't that damaging the equipment? I understand that this level will be lower very soon due to the chlorine being used, however it seems like an insane amount of chlorine to add. 

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Agreed.

That 7 ppm per person per hour is only an approximate figure, and probably assumes 40 degrees celcius. First, different people produce different amounts of bather waste for the same time and temperature. Second, the ppm used by one person depends on the size of the tub as one person in a large tub will use less ppm per hour than in a small tub. Also, bather waste goes down significantly as the temperature goes down. For instance at 102 deg F I will perspire fairly heavily; at 101 deg F moderately heavily; at 100 deg F only moderately; and at 99 deg F I will perspire fairly lightly. 37 deg C is 98.6 deg F, so at the temperature you are using, I would not expect the bather load to be anywhere close to 7 ppm per person per hour. I can't really name a number, but I would guess it is much closer to 1 or 2 or 3 ppm per person per hour at that temperature.

My wife and I love the use of chlorine in the tub. We've only been in it 4 times so far, but there is no smell of chlorine, and my wife, who is extremely sensitive, does not even get an itchy nose, which she did with bromine. The chlorine demand of my tub is about 20% to 25% in 24 hours. I found that when we soaked for 30 minutes at 100 deg F I had to add a total of 5 ppm of chlorine. My tub is only 230 gallons so we use the chlorine up faster than we would in a larger tub. If 25% of that 5 ppm is chlorine demand of the tub, then the bather waste is taking 3.75 ppm per person per hour at 38 degrees celcius.

The best way to find out is by doing some testing yourself. Take a chlorine reading right before you get in, then take one after one hour. Also, take a reading the next day at the same time you took the reading before you got in (24 hours later). Let's say you started at 6 ppm before getting in the tub, soaked with 4 people for 2 hours (8 person hours) and then added, lets say for argument sake, 20 ppm of bleach after everyone is out. Then let's say the reading 24 hours after the start of the soak turned out to be 6 ppm. Then you would know that your bather waste plus 24 hour chlorine demand was in this example 20 ppm. If your tub's chlorine demand is as low as 25%, then the bather waste would be in this example 20 - 4.5 or 15.5 ppm. You can also test the same day after soaking. If you take a reading before you get in the tub, then soak, then add chlorine after you leave the tub, and wait maybe one or two hours for the bather waste to all be neutralized, then take another reading, this should give you a pretty close measure of the actual bather waste.

You should use bleach after the bathers are out of the tub, or at least a few minutes before the bathers enter the tub, but not while the bathers are in the tub. However,  you can use MPS non-chlorine shock while the bathers are in the tub, so if through testing you find that the bather waste chlorine demand is taking the chlorine down to zero during the soak, you could use MPS to prevent this. MPS will oxidize bather waste directly, but will not increase the chlorine, so you would have to add it before the chlorine is all depleted.

If while you are testing and gathering information, you find that the chlorine actually gets down to zero while you have people in the tub, don't worry about it being a health issue as long as you get the chlorine level back up fairly quickly, and keep it above the minimum level the rest of the time.

The recommended level of CYA for a hot tub is 30 ppm or 40 ppm. I think in your situation 40 ppm makes more sense, because more chlorine is bound so it will last longer. Under your circumstances, after doing your testing, you may even want to go to 50 ppm CYA if your bather waste chlorine demand is very high. I actually have by calculation 34 ppm CYA in my tub now, and am using only bleach.

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Thanks for helping me understand this! I didn't know temperature has that kind of impact on the generated bather waste. Your example calculation makes sense.

I think the first time that I expect to be in the spa for like 2 hours with 4 people I will just make sure to start a little high on the FC. And then after soaking I will test the FC after 1 - 2 hours as you suggested, to see how much is used up, just to make sure it doesn't get to zero all night. Since 37 degrees celcius is not too high of a temperature (I don't have the feeling that I am sweating much at this temperature), I don't expect to burn through the FC very rapidly. I think once I have had a couple of tub sessions and done measurement before and after, I will very quickly get a feeling on how fast the FC is being used up on a typical session.

I think I will start to bring my CYA to 40ppm to start with and see how it goes. 

As for the MPS non-chlorine shock during heavy bather sessions, I have searched for this product over here but I cannot find it. However, if I really expect heavy bather sessions and I am afraid my FC will fall to zero for some time, then I'll probably put a HTH briquette (7 gram per puck) in a floater during the bather session. This mostly adds calcium hypochlorite. Or do you think it would be a bad (health-wise) idea to have this floating around while we are in the tub? Because I have read that chlorine without CYA is too strong for application, so wouldn't these HTH briquettes be to strong? I understand that there is CYA in the water so it won't be an issue once it has been mixed in the water, but since we are dissolving nearly 7gram of calcium hypochlorite directly to the water we are currently in, I don't know if it could be dangerous / too strong for a moment. 

It's very reassuring that you and your wife are liking the chlorine treatment. I can't wait to finally start using the dichlor-bleach method myself. I will drain and fill the tub this week. I'll let you know how it turned out for us. 

 

 

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I don't know if cal hypo in a floater would be a little harsh on the skin. You generally see the recommendation to remove the floater while people are in the tub. Also, I don't know how quickly that brick of cal hypo will dissolve. It may take a while, not sure. If it goes pretty slow, it would be safer.

In my opinion, it should be safe to use the tub down to zero free chlorine, as long as you add bleach immediately after exiting the tub, and keep the free chlorine level above the minimum at all other times. In that case, the amount of time that the water would be below correct sanitation level would be relatively short, and unless someone in the tub is actively sick and contributing bacteria, I would think it would be fine for an hour or so.

How much chlorine you need by parts per million does vary with the size of the tub. But there is another way of computing this. See this post on TFP forum, in particular the next to last paragraph. Again, the numbers given are for 40 degrees celcius, so need to be adjusted for temperature.

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I don't think the cal hypo tab would dissolve really quickly, because I put it in a slow dispenser floater. I checked the poolcalculator and in my tub size 1 tab of 7 gram will do this:
- raise FC by 3.6, CH by 2.6 , Salt by 3.7. Does not seem like a shocking amount of chlorine, especially since it dissolves slowly I guess the change of it being harsh on the skin is minimal. But I will make sure to check out the instructions for the briquettes to double check. 

I read some warnings in several post about never letting the FC drop to zero. Everyone getting in our tub is asked to shower before, we don't eat in the tub and the tub is not too hot. So I think that lowers the chances of dropping to zero unexpectedly fast, and if it does I will make sure to get the FC level up as soon as possible once we're out the tub. Like you I don't expect dropping to zero for a short time is too big of a problem if everyong is clean and not contributing diseases to the water :) 

I read chem geeks post from your link. Do I understand correctly that at 40 degrees celcius, 5 fluid ounces of 6% bleach would kill one hour bather waste? It would make sense, because no matter the size of the tub I produce an X amount of bather waste at a certain temp. In my case at 37 degrees celcius this will of course be less, but I'll find out by testing it a few times. 

Draining my tub today btw :D

One quick thing on which I am wondering how others / you do this: what if you go away for like 5 days and your 24-hour chlorine demand (baseline) is close to 35% for example. This would mean that in like 3 days my FC would run to zero (right?). In such situation I would make sure the level FC is a bit higher then usual before my leave. Would it also help to put the water temperature a little down? Or does that only help when you're in the tub (for sweating etcetera)?

Also, thanks so much for the time you took to help me out and share your knowledge. I wanted to let you know I really appreciate it and I gained so much knowledge the last couple weeks! 

 

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On chem geek's post, yes, that was the reason I posted it so you could see that relationship. At 37 degrees your figure might be (strictly guessing here) somewhere around 20% to 40% of that figure.

Being away for a period of time has always been a problem for tub owners who use chlorine. The only solutions I have read about are using a floater or using a salt water chlorine generator or getting someone reliable to add chlorine for you while you're gone. You might want to research the chlorine generators and how they work. Here's an interesting post from the TFP forum.

By the way, those cal hypo tabs at 7 g would be pretty small. Your floater undoubtedly will hold a bunch of them at a time. You can regulate the amount of chlorine you are adding per hour by both the number of tabs in the floater, and the floater setting itself. When I used bromine, I would have usually 5 or 6 1-inch bromine tabs in the floater and the floater door fully open.

Thank you for the  kind words, and it has certainly been my pleasure to help out. I hope you and your family and friends get much enjoyment from your tub.

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Thanks! Also thanks for the chlorine generator, once it becomes an issue I will maybe look into that. For now I have no plans to leave for a long time, so I will be fine :)

Btw, I drained the tub and refilled. After lowering TA and adding borates, I shocked to 9 - 10 ppm FC . I checked an hour ago (which is like 14 hours after refill) and the

  • FC was 2,5ppm
  • CC was 1ppm

I know you want CC to be as close to zero as possible. The chlorine smell from my spa is quite strong too at the moment. Do you have any advice on this? Is this because this is only the first shock and will the CC to FC ratio be better after a few shocks or maybe once I have more CYA in the spa?

Also, I did go from 10ppm to 2,5ppm in 14 hours. That's quite a drop, but I guess it is because of the dirt(y water) that was still in my pipes. The first time I put the jets on after refill I literally saw greasy, cloudy water being pumped in the pool. I will check the chlorine demand again after my next shock to see if I burn through the FC less speedy then. 

Last quick question: for the FAS-DPD test I need to add a powder to my water. However, it says to add a heaping dipper of R-0870. There is not too much powder in my R-0870 tube. If I test my chlorine level every 2 days for example, I will burn through all R-0870 powder within weeks I guess.. The stuff is pretty expensive to get shipped here so I was hoping it'd last way longer. Any ideas on this? Or am I using way to much R-0870

Thanks again, and we will certainly enjoy our tub! 

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I feel stupid, I just did another chlorine test and now I understand why I thought I would burn through my R-0870 so fast. I used the wrong side of the dipper :) Last time I added 2 spoons of the big side. O, and I cleaned my filter. It was quite greasy, the filter looked a little bit brown and once I cleaned the filter it looked way cleaner, so I guess that will help the FC drop less faster too.

Also, I read some articles about high CC levels and if I understood correctly I need to keep shocking in order to get it down. Sounds strange, but what do I know :) I just shocked it to 10ppm again (actually, I tested directly afterwards and it was 11ppm, so maybe my tub has a little bit less volume then I was thinking). 

Anyway, if you have inspirational ideas let me know. For now I will continue shocking the tub untill the CC has dropped a bit. 2 more shocks and I need to switch too bleach anyway because of the CYA level (I am at 19 now, calculated not tested).

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Combined chlorine of 1 would indicate that the chlorine is oxidizing quite a bit of material. In my tub, I know the water was pretty clean after the refill. I used "ahh-some Hot Tub/Jetted Bath Plumbing & Jet Cleaner" to purge the plumbing before I drained the old water out. Then, due to an error on my part, I took the free chlorine up way higher than I intended, resulting is us having to wait almost a week before using the tub after filling. FC was initially 23 ppm after refill. The combination of those two things meant that the combined chlorine was 0 every time I checked it before the first week was up. After we started using the tub, combined chlorine has remained less than 0.5 every day. After I get the sample water to clear, and add back the 5 drops of DPD reagent #3, the sample turns just the very faintest of pink. I think you must have a residual of stuff in your tub. No telling what or how much but your weren't using an approved sanitizer (here is the US). You might want to read up on bio-film and it's effect on hot tubs. In the mean time, I would continue shocking until you get the combined chlorine down to 0.5 or below. Make sure you are using the correct shock level for your CYA. The chlorine smell will be both from the combined chlorine, and the shock level of chlorine. Currently, with FC around 5 ppm plus or minus, when I first open the lid I will smell a little chlorine in the moist air that first escapes, but when we get in, we can't smell it.

You don't need very much R0870. In a 10 ml sample, I use only one very slightly rounded small dipper of the powder. The guideline the manufacturer gives is a bit of overkill in my opinion, but they have to make sure that everyone gets valid results with their test. You only need enough to react with all of the chlorine in the sample. At 5 ppm even less than a full dipper would probably do it. There is supposed to be enough powder in the vial to do over 100 tests, even at the higher 2 scoop per sample usage amounts.

For pools, on TFP forum, they call it SLAMing the pool. It means Shock Level and Maintain. In other words, bring the water to shock level for the CYA level, and keep it there constantly until the foreign substances (usually algae in the case of pools) is completely removed. There is a test for pools, but I don't think it applies exactly to tubs. But the test is 1) water is clear 2) CC is 0.5 or below 3) overnight chlorine loss test is less than 1 ppm. I think 1 and 2 definitely apply to a tub, but 3 might not be possible because of the temperature of the water causing the FC to dissipate more than in a pool. Even if your tub's 24 hour chlorine demand is 50%, your overnight (12 hour) loss would be no more than 2 ppm if you started at 8 ppm. If your chlorine demand was 25%, the overnight loss would be 1 ppm if you started at 8 ppm.

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Thanks so much as always! 

Last night I shocked the tub to 10ppm. I checked again this morning, 14 hours later. The FC had dropped 60%. I have an ozonator, so I read that this could cause higher percentage. But it's a lot better then the 80% I was at the day before. And the good thing is, the CC level is .5 or even lower, so that's a good thing. The chlorine smell is way less too. 

I'll keep checking the FC and CC levels to see how it goes, but I feel it's heading in the right direction. The water is clearer then it's ever been too btw. Only thing that occurs is a little bit of foaming (like solid foam I can pick up and throw out). I read that it might be caused by low CH level, my levels is somewhere between 120-130ppm. Should be fine I guess. My CSI is a bit too low (-0.15). But I have lowered my TA to something like 70 (will measure today). It's the only way my PH stays in reasonable range (7.6 - 7.7). But the low TA is causing a lower CSI as well. Looking at the poolcalculator, the only thing to get my CSI closer to zero is adding more CH. Would you advise to do this? Because I don't have much room in the TA, since that will get my PH too much out of balance. 

Thanks for the SLAMing information, I read all about it now. I'll see where my CC stays at now and if it get's too high I will maybe try SLAMing. For now the shock last night to 10ppm seem to have worked out very well. 

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After a week of using the tub, my wife smelled chlorine for the first time last night. Yesterday afternoon when I checked, the FC was at 5.5 ppm,  CC < 0.5. We soaked as usual and at the end of our soak, we turned on the air for a minute. That's when she smelled the chlorine as the bubbles caused the water vapor to increase, so she asked me to turn off the air. We've used the  air a few times this past week without smelling the chlorine though.

With a fresh fill in a chlorine tub, you should not be experiencing any foaming at all. That you have solid foam you can pick up indicates that there is still foreign material in the water. It may take a little time, but eventually the chlorine will react with all of that material, whatever it is. In our tub, when the air is turned on, the water pump is turned off and a lot of air is injected into the water. The tub, which is a round inflatable, has a ring around the base that has holes in it about every 3/4 inch or so. So much air makes the water really move around fast. It actually works very well for mixing chemicals in. When we had bromine in the tub, and after several months of using the tub, we would get foam when the air was running. The foam would build up to as much as 3 or 4 inches deep in the center of the tub, and would be a white bubbly foam that would dissipate completely in less than a minute once the air was turned off. That kind of foam is not uncommon in hot tubs. I think it comes from excessive dissolved solids in the water. One time in the six months of using bromine, we had guests in the tub who used bathing suits which apparently contained a significant amount of soap. After that soak, we had a serious foaming problem, billows of foam that would not dissipate. I shocked the water and then kept the bromine level elevated above recommended levels for a couple of weeks, and eventually that foam from soap was all gone. In our chlorine tub with the water still fresh, there is absolutely no foam when we run the air. Calcium hardness of at least 100 to 150 ppm helps to prevent the soap caused type of foaming.

Yes, we discussed your ozonator earlier. I guess you can't turn it off temporarily? Is there a way you could disable it temporarily, like unplugging it from the control board or something? While running, it will increase the chlorine demand.

The recommended level for CSI is between -0.6 and +0.6. They say the closer to zero, the better. That's a fairly wide range, however, and probably not a serious problem if outside those numbers by a little bit. Most hot tubs are not plaster so CSI is only critical for the health of the equipment. Extremely high positive CSI might encourage calcium buildup in the heater and pipes. Extremely low CSI might accelerate the corrosion of metals inside the equipment. Actually, a CSI of -0.15 is quite good. I would rather have it a bit on the low side. My CSI is currently -0.44, pH 7.4, TA 60, CH 150, CYA 34, borates 55.

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I am curious if turning on the airjets will cause much chlorine smell in our tub. I was very (happily) surprised this morning that the chlorine smell (after opening the lit a minute or two) was way, way less then yesterday. I don't mind a little chlorine smell by the way.

Ok, the foaming is weird then. My CH is 120 at the moment, will maybe increase it a little bit just to be sure. Will help me getting closer to 0 CSI as well, so it's a win-win. Our tub has air-jets as well as water-jets, if I put everything on it gets mixed really well, really fast too. At the moment both the water jets and the air jets cause foaming. It must be something in the water indeed, I will just keep maintaining the balance and chlorine like I do now and see if it goes away.

I cannot turn off the ozonator as far as I know. I will check the manual soon to see if it says anything about it. But I think I will manage with ozonator as well, at least it helps killing bacteria when there's a bunch of people in the tub. 

As for the CSI, good to know it is not really a big deal to be a little off because it is pretty hard to get it real close to zero :) 

Thanks again, I think I am on the right track with everything. I am getting the hang of testing and dosing chemicals. I feel like I have way more control then I had with the products I used before, because now I actually know and understand what chemicals are being put in the tub (and why I am putting chemicals in the tub). 

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Hi Mpurcell,

My water maintenance is going great! It is taking up some time at the moment, but it's all new so it takes time to get adjusted to it. My CYA is now 35, CH 150, TA 70-80, PH stable around 7.55-7.65 (digital PH meter). So, I am where I want to be for the most parameters. I will stay at CYA 35 for now and see how things goes. The water is still crystal clear. It does foam a little bit (it is less then before) and after the foam is gone it leaves a little bit of white-ish residu on the surface. However, that's gone within a minute (if the tub is filtering). Don't know what that is, but maybe it will just take a little more time.

So, since my CYA is now at 35, I am going to switch to bleach. I already added a 150ml of bleach this morning. The hard thing is, the bleach only says <5% sodiumhypochlorite. So I don't know if it's 1, 2 or 5. I will see if I can e-mail the manufacturer to get to know a more specific percentage, but do you have any advise on how to handle this? Is there maybe an easy way to check the percentage of sodiumhypochloriet in bleach? I was thinking, maybe I should check my FC level. Then add like 100ml bleach. Let it all mix for 30 minutes, and check my FC level again. That way I would know what 100ml bleach does. However, I am not sure if every bottle of bleach has the same concentration, so it's a bit hard to work with.. And it seems impossible to get >5% bleach over here.

Thanks!

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By the way, after searching for a little while I found that there are some shops over here selling 'Natriumhypochlorite 12,5%'. Would that be good to use in my spa? They sell it as 'Liquid chlorine'. Is that stuff good for sanitation? Here's a MSDS: https://www.odnzkg.nl/mozard/document/docnr/1484130,,3739471,/Bijlage 13 Natriumhypochloriet.pdf .pdf

It seems like the right stuff to me, but I don't want damage to my spa so I am double checking. And if this is good, can I put it directly into my tub, or is it better to first put it in a bucket of pool water so the concentration of the liquid gets lower? 

 

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Your plan to determine the strength of the bleach is correct, and the best way to proceed with that bleach as far as I can think.

We have 12.5% liquid chlorine in the US as well. It is a fairly common product in pool stores, and is exactly the same thing as bleach, except more concentrated. There is an option for 12.5% in pool math. You'll carry a lot less weight around if you buy the liquid chlorine. I think it is exactly what you were looking for.

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