chem geek
-
Posts
5,297 -
Joined
-
Last visited
-
Days Won
1
Posts posted by chem geek
-
-
Why don't spa owners use liquid chlorine and so forth in tubs like a regular pool?
Some do. Some spa owners use Dichlor and/or bleach. Others use bromine and some use Biguanide (PHMB aka Baquacil). There are advantages and disadvantages to each. Other pool chemicals, specifically baking soda (sodium bicarbonate or Alkalinity Up) are also used for pH buffering. Calcium is not usually added since tubs are not usually plaster.
-
Ah thanks for thinking about that. Yes, the dihydrate form of Dichlor, which is the most common, is 55.4% available chlorine (usually quoted as 56% as you indicated) while the anhydrous form of Dichlor is 64.5% available chlorine (quoted as 62% in your example). The ingredients label will list the weight percentage of each chemical and probably says nearly 100% of "Sodium dichloro-s-triazinetrione dihydrate" or something like that. There may be a separate entry that says "XX% Available Chlorine".
And yes, for every 1 ppm FC added by Dichlor, it will also add 0.9 ppm to Cyanuric Acid (CYA) levels.
-
I don't know what is in the other stuff. I you have a specific brand, then I can try and look up the MSDS to see what is in it or you can read the ingredients label, but it may just say "inert ingredients". Dichlor isn't that expensive -- you can get it a Leslie's online for $2.60 per pound and for spa amounts that's way more than you need. You should only use Dichlor for about a week after a fresh water fill and then switch to bleach after that. Otherwise, the Cyanuric Acid (CYA) level will keep building up making the chlorine less and less effective and unable to kill the bacteria that causes hot tub itch. Most people don't get that, however, so you can just use Dichlor if you want -- I'm just giving you a conservative option.
The most common form of Dichlor is dihydrate (as opposed to anhydrous) and I didn't even know they made any Dichlor less than 100% pure.
-
Generally speaking, properly maintained outdoor pools exposed to sunlight that maintain sufficient chlorine levels relative to their CYA levels (minimum FC at all times of 7.5% of the CYA level; target FC around 11.5% of the CYA level) hardly ever need to be shocked. If you get a good FAS-DPD chlorine test kit, such as the Taylor K-2006 (not the K-2005), it will test for Free Chlorine (FC) and Combined Chlorine (CC) accurately. You only need to shock if the CC level goes up (usually above 0.5 ppm is when shocking is needed), but in my own pool, for example, it rarely gets above 0.2 ppm. Sunlight helps break down combined chlorine and the proper chlorine levels continually oxidize organics. After a heavy bather load, there may be a need to shock, but raising the FC level prior to the bather load also works.
The only other times to shock are if the water starts to turn dull or cloudy, usually if the FC level went too low, or if there is an algae bloom. If there is an "accident" in the pool, then a shock is needed.
-
Yes, the newer MA is twice as strong as the old. It used to be that all Muriatic Acid for pools was 31.45% so the 29% is at least close to that. At some point, someone figured out to sell 15-16% MA at the same price and several users have reported that around the country so you really have to read the labels carefully. The main advantage to the lower concentration is that is should fume less so be less noxious -- it's probably the harshest chemical added to a pool.
-
Terri,
With the CYA at 36 ppm (are you estimating that from the K-2006 kit, reading between the lines, so to speak?) the minimum chlorine level would be 2.7 ppm with a decent target FC of 4.2 ppm so your chlorine level does seem fine at the start of the day unless you had mustard/yellow algae (which it doesn't sound like you have). However, it does sound like the FC level does drop below the minimum by the end of the day and that's not good (you reported 2.2 ppm FC at 4 PM).
Though it is true that dull water and then cloudiness can be from algae growth, the fact that you only see this cloudiness occur when you try and raise your pH by using pH Up tells me that this is just the normal situation of having a pool that is close to saturation in calcium carbonate (your pool's saturation index is around -0.2 when the pH is at 7.3 with the other numbers you reported). pH Up is identical to Arm & Hammer Super Washing Soda (careful: not the detergent) and is Sodium Carbonate. In the local area where it is added, it raises the pH quite a bit and also increases the Total Alkalinity (TA) by quite a lot (it adds a lot of carbonates). This makes the water cloudy. In fact, if you add it too quickly, you can even get solid pieces of calcium carbonate that fall to the bottom of the pool. Eventually, the cloudiness dissipates (usually over a day) and that seems to be what you are seeing and this is perfectly normal.
If you are using bleach or chlorinating liquid as your normal source of chlorine, then you do not need to have the TA be higher, so I'm guessing with the low pH that you had that you might be using Trichlor pucks/tabs, is that right? If so, then you need to not use them for too long as your CYA will climb (unless you do a LOT of backwashing regularly or have lots of splash-out). At any rate, most of the cloudiness you see appears normal. If you want to raise the pH without raising the TA as much nor have as much cloudiness, you can use 20 Mule Team Borax instead -- you use twice as much by weight to get the same effect as with pH Up. Or if you want to raise the pH with no change in TA at all, then just aerate the water and do not use an acidic source of chlorine (i.e. Trichlor).
If you want to know if you have algae, see if the Free Chlorine level drops overnight more than 0.5 ppm or 1.0 ppm. If it does, then you've got algae or some organics using up the chlorine and will need to shock the pool with higher chlorine levels -- 40% of the CYA level or about 15 ppm FC in your case -- using unscented bleach or chlorinating liquid. In any event, be sure to not let your chlorine drop below 7.5% of the CYA level ever. You might need a higher CYA level and correspondingly higher FC target to keep the chlorine from getting broken down as quickly by the sun, but before going that route make sure you aren't just using up the chlorine by a nascent algae bloom. You have reported some Combined Chlorine (CC), but not so much to be of concern (< 0.5 ppm is usually OK, though typically one measures only 0.2 ppm except after moderate to heavy bather load).
Richard
-
I know there are disagreements about this, but switch to using bleach after you've added a week or so of Dichlor to the hot tub. If you use only Dichlor for the entire 3 months before you drain/refill, then the CYA level will build up and the chlorine will become less effective as a disinfectant. This is why some health departments recommend not using Dichlor (see this link). I think that's too extreme and a balanced approach of using some Dichlor first to get some CYA in the water is wise and helps keep down the chlorine outgassing (smell and usage), but like anything else, too much (of CYA in this case) is not good.
For every 1 ppm FC added by Dichlor, it also adds 0.9 ppm CYA. So it doesn't take long to build up, especially if you use the tub frequently.
By the way, of the four people who reported hot tub itch and to whom I suggested not using only Dichlor (they all used only Dichlor previously), one said it worked, another said it didn't (i.e. they still got itching), and two didn't get back to me. So it's inconclusive as to whether the higher disinfecting chlorine level by only using Dichlor briefly and then switching to bleach will really work against that bacteria. It clearly is better overall for disinfection, but most bacteria are very easy to kill except for the one that causes hot tub itch.
Richard
-
Your welcome. Just remember that it's the chlorine (especially at shock levels) that kills the algae. The PolyQuat 60 is slow-acting so is best as a preventative or insurance policy against algae. At least now you know where the CYA came from so you can monitor it better in the future and use appropriate sources of chlorine. Good luck and enjoy swimming!
-
Ozone would oxidize bromide to bromate (see this Wikipedia link for the reaction). Notice that it isn't bromine (hypobromous acid) that gets oxidized, but rather bromide. Bromide is what bromine gets reduced to when it disinfects or oxidizes. So IF there is an additional oxidizer (shock) in the water such as chlorine or a non-chlorine shock (potassium monopersulfate), then the bromide should get restored to bromine and there should be very little bromide in the water. So I suspect that though some bromate is formed by the ozonator, that it doesn't happen as much so bromine usage is probably not seen as dropping in bromine spas with an ozonator, especially if they are co-maintained with chlorine (some floating feeder bromine products introduce both bromine and chlorine into the spa simultaneously) or shocked regularly. On the other hand, bromates are somewhat more of a health issue than chromates, but unless you are drinking the spa water this may not be a big issue.
As for the hazards of ozone itself, I think that in spas with decent ventilation there isn't that much of an issue and the dealer is correct that most of the ozone will react very, very quickly in the water -- ozone is not very stable which is why it is so reactive. If there was ozone in the air, you'd smell it. It's not odorless and if you've ever smelled electrical sparks, then you've smelled ozone. The good news with ozone is that it will kill even hard-to-kill bugs such as the bacteria that causes hot tub itch. The bad news is that it does not leave a residual for disinfection in the main body of pool water so you still need to use something there and unfortunately no matter what you use ozone will react with it, at least a little.
-
In addition to the problems with ozone that were mentioned, the part about needing less chlorine is interesting (and probably wrong) because ozone itself destroys chlorine so that in some systems you end up needing more chlorine with the ozonator running. See this link for the chemistry behind ozone being a stronger oxidizer than chlorine and therefore oxidizing it to chlorate (with the ozone becoming oxygen).
-
If the Cyanuric Acid (CYA) level is really 100-150, then you are going to have a hell of a time keeping your pool free from algae unless you use a initial dose and then a weekly dose of PolyQuat 60 algaecide (for preventing algae -- it's not that good at stopping an algae bloom already in progress). Otherwise, you'd have to keep an absolute minimum of 7.5 - 11.2 Free Chlorine (FC) level (depending on the actual CYA level) to keep away algae. You said you used algaecide -- what kind and was it used in a weekly maintenance mode or just on occasion?
As for clearing up the algae that is already starting -- which is what makes pool water initially look dull, then cloudy, and eventually full on green bloom -- you need to shock with chlorine, but it will take extraordinarily high levels given the high CYA level. So you can certainly shock now to at list slow down or stop continued growth, but you are going to have to do a partial drain/refill to lower your CYA level eventually anyway IF you don't want to use an algaecide nor keep very high chlorine levels. You'll have to do at least a 50% dilution since you'll want your CYA level to be closer to 50 ppm (typical is 30-50 except for saltwater chlorine generator pools at 60-80 because they are regularly adding chlorine and super-chlorinate in the cell so have less risk of developing algae even at lower disinfecting chlorine levels).
Your pool is above-ground so probably vinyl, but if you had a plaster pool then high CYA levels above around 150 could damage the plaster as well (see this link).
To avoid having the CYA rise so much in the future, realize that Trichlor pucks/tabs and Dichlor powder/granules both add Cyanuric Acid (CYA) to the water in addition to chlorine. For every 1 ppm FC added by Trichlor, it also adds 0.6 ppm CYA. For every 1 ppm FC added by Dichlor, it also adds 0.9 ppm CYA. So unless you have a lot of splash-out or lots of backwashing in a smaller pool, the CYA level can build up rather quickly over just one season. Cal-Hypo does not have CYA (but needs to be pre-dissolved in a bucket of water before adding to the pool) but does add to Calcium Hardness (CH) where for every 1 ppm FC added by Cal-Hypo it also adds 0.7 ppm CH. However, this is a smaller percentage of typical CH and in vinyl pools the CH is usually lower anyway so one can usually use Cal-Hypo at least longer than they can use the stabilized chlorine products (Trichor and Dichlor).
Unscented bleach (e.g. Clorox Regular or off-brand Ultra) and chlorinating liquid do not add to CYA nor to CH so are a more pure source of chlorine, though they do add extra salt (ALL sources of chlorine add 0.8 ppm salt for every 1 ppm FC when the chlorine gets used up, but bleach and chlorinating liquid add an additional 0.8 ppm salt on top of that). If you add these liquid sources of chlorine to a vinyl pool, be very careful as you must add it very slowly, preferably over the water flow from a return (in the deep end, if more than one) and for extra safety you can brush the pool bottom near where you pour afterwards and can pre-dilute the chlorine in a bucket of pool water before pouring. The chlorine is denser than water so you don't want it settling to the bottom of the above-ground pool that typically does not have a floor drain so has poor circulation at the bottom (this is also why you pre-dissolve Cal-Hypo so it does not settle at the bottom of the pool).
Richard
-
It it near colorless to light yellow, depending on concentration, but typical Muriatic Acid is light yellow. If you had chlorine instead, it would be closer to green and you can tell the difference right away since Muriatic Acid does not smell like chlorine and is in some ways even more irritating (just use your hand to waft fumes from an open bottle towards your face and you should be able to smell what it is).
As for being a deep yellow, that does sound strange, but doesn't sound like chlorine. It may just be a more contaminated form of Muriatic Acid.
Your pool can still experience a rise in pH after adding acid if it is high in Total Alkalinity (TA) and/or has a source of aeration such as waterfalls, spillovers, fountains, showers and especially a saltwater chlorine generator (SWG) since that produces hydrogen gas bubbles that pull out lots of the carbon dioxide from the water and into the air and that causes the pH to rise (it's a myth that the reason SWG pools rise in pH is due to the added chlorine -- chlorine is alkaline/basic when added, but chlorine usage is acidic and exactly compensates so hypochlorite sources of chlorine as well as SWG-generated chlorine are essentially pH neutral).
Richard
-
16 grains is 274 ppm Total Hardness (you multiply by 17.1 to convert from grains to ppm CaCO3 equivalent). The Calcium Hardness is probably around 200 ppm as the bulk of the hardness is typically calcium with the rest being magnesium, but this depends on the water source. waterbear can address your other questions.
-
Your chlorine is low, but it sounds like you've added some more to compensate for that. Your pH and TA are high which would account for the cloudiness as well. The calcium carbonate saturation index is around +1.2 which is very high so even adding chlorine can make that even more cloudy temporarily due to the rise in pH. You really need to get your pH and TA lowered and you can do that by following the Lowering Your Alkalinity procedure on the TFP site (I'm at that site as well) which is described in this post. The folks at TFP will be able to help you through this. Just make sure your Free Chlorine stays at around 4 ppm FC though you can shock at higher levels of around 14 ppm FC in case there is any algae starting to develop. You can add acid to lower the pH right away and start aerating.
I calculate it will take 104 fluid ounces of Muriatic Acid to lower the pH to 7.2, but add less and see where you are at. You then aerate until the pH gets to 7.4 and then add acid to get back down to 7.2 (about 26 fluid ounces of acid initially; the amount will drop each cycle as the TA gets lowered). Not counting the initial 104 ounces of acid, it will take an additional 340 ounces (42-1/2 cups) to get the TA to 80 from the initial 204. So it takes a lot of acid and aeration to lower the TA. How did the TA get so high in the first place? You should test your fill water to make sure it isn't so high in TA.
Even if you just add acid to lower your pH, that should significantly reduce the cloudiness.
Richard
-
Well, your use of Dichlor explains the high CYA level. For every 1 ppm Free Chlorine (FC) you were adding with Dichlor, you were also adding 0.9 ppm Cyanuric Acid (CYA). The Dichlor also explains the low pH because in spite of what pool store folks think, the use of Dichlor is actually acidic (Dichlor addition is only slightly acidic, but the use of chlorine is acidic so the net result is acidic). Since you've got metals in your well water and don't want to do a partial drain/refill, then I suggest you use a PolyQuat 60 algaecide to keep away algae. Before that is done, we've got to get rid of whatever algae is there which may be causing the cloudiness. So don't worry too much about the pH right now since it will rise on its own now that you have stopped using the Dichlor. Go ahead and add the chlorine (unscented bleach or chlorinating liquid) as I suggested to get your chlorine level up higher to around 15 ppm FC and keep it there, which means regular testing and adding more chlorine. This should get your water to clear though it may take a day or two (if it's not too cloudy). You can not only churn the water to mix the chlorine when you add it, but you can also aerate it by pushing the pool brush down into the water from the surface which, when I do this, makes lots of bubbles.
You are going to have a difficult time accurately measuring 15 ppm FC with your drop test. You can try and use the dilution method since your test kit will only measure to 5 ppm, but that's not very accurate. If you can, see about getting the Taylor K-2006 test kit anywhere you can, but most pool stores don't carry it (some carry the K-2005, but that's a 5-drop compare the color test like you already have). The Taylor K-2006 is available a bunch of places online including from Taylor here and from Leslie's here and there is an even better kit based on the Taylor kit but using a more logical size of reagents called the TF-100 from tftestkits.com here. With these kits, the chlorine test is a FAS-DPD test where you add 2 scoops of powder to make the sample turn pink (if there is any chlorine) and then add titrant drops and simply count how many until the sample turns completely clear. You then multiply the number of drops by 0.2 or 0.5 depending on sample size to get Free Chlorine (FC) -- that's it. Very easy and very accurate. No comparing of colors. And it can measure up to 50 ppm FC. You then add another reagent and if there is Combined Chlorine (CC) it turns pink again, then add titrant drops and count them and you get your Combined Chlorine number. Very foolproof. It's the kit that all pool stores should have and also tests pH, Total Alkalinity (TA), Cyanuric Acid (CYA) and Calcium Hardness (CH).
I think the higher chlorine levels will help your situation. Once you've made your water clear and you have no loss of FC overnight and no measurable CC, then you can just maintain 9 ppm FC if you can and add PolyQuat 60 algaecide so that even if the chlorine is lower, you won't get algae (you'll add a maintenance dose of this algaecide every week). This will hold you over until you are able to lower your CYA through dilution or you can just stick with this, but will be more costly due to the algaecide.
See if maintaining the 15 ppm FC and mixing of pool water clears things up -- I wouldn't turn off the pump or use a floc just yet. Your pool didn't sound that cloudy so the chlorine may be able to break everything down on its own and not need physical removal of dead algae. If it appears that the algae isn't dying -- if the green remains, then raise the FC more up to 25 ppm -- with your 80 ppm CYA this isn't actually very high in chlorine even though it sounds like it is -- the CYA attaches to most of the chlorine making it less potent to everything (liner included). To play it safe, measure the CYA with your own test kit before raising the FC above 15 -- the pool store could be wrong, though the high CYA does make sense given the Dichlor usage.
Richard
-
If he didn't check the Cyanuric Acid (CYA) level before figuring out what to do for shocking -- that is, what level of Free Chlorine (FC) to get to and then maintain through frequent checking and addition, then he hasn't done anything. Algae can be cleared with chlorine alone as can be seen in this link that shows a pool with lots of algae upon spring opening getting cleared by using chlorine. If the CYA level is very high -- well above 50 ppm or even 100 ppm or more -- then a partial drain/refill to lower the CYA level is in order. Then you'll be able to attack the algae with far lower levels of chlorine. The fast shock level of chlorine is an FC level that is 40% of the CYA level, but you need an FC level of at least 20% of the CYA level to even have a hope of keeping up with the algae and kill it faster than it reproduces. This is why knowing the CYA level is so important.
If the pool is no longer green and it's just dead algae and looks cloudy, then if you have an above-ground pool with no floor drain and poor circulation, then a flocculant can be used to consolidate the particles and then you vacuum to waste to remove them, but you only do this AFTER you've killed all the algae and it sound like that hasn't been done yet.
If your pool guy doesn't know about the Taylor K-2006 test kit, then get that yourself from Taylor here or from Leslie's here or get the even better test kit TF-100 from tftestkits.com here. It sounds like you may need a new pool guy who can handle the situation -- you. It's really not that hard and certainly will be less expensive (depending on what you charge yourself
).Richard
-
Your pool water volume for your 18' diameter, 48" deep round pool is 3.14*(18/2)^2*(48/12) = 1018 cubic feet = 7615 gallons so let's call it 7600 gallons.
You want to raise the pH without raising the Total Alkalinity. The only way to do that is with aeration so if you have any aeration features such as waterfalls, spillovers, fountains, showers then you should turn those on. Hooking up a pool cover pump to a shower also works or using an air compressor/pump with a nozzle or pipe to produce lots of tiny bubbles and putting that end into the deep end of the pool works really well.
If you can't aerate the pool, then using Borax would be the next best thing since it won't raise the TA by too much. You would need 5.6 pounds (90 ounces weight) of 20 Mule Team Borax which is about 1.2 boxes (since each box is 76 ounces weight and you need 90). It's probably about 11 cups in volume assuming one box is around 9 cups in volume. This amount of Borax will raise the pH to 7.5 and the TA to 174. So you can see why aeration would be better since it won't raise the TA at all.
Baking Soda is used to raise the TA and only raises the pH a small amount so you definitely do not want to add that.
Your Cyanuric Acid (CYA) level is high and your Free Chlorine (FC) level is too low. You need to target an FC level of 11.5% of your CYA level, so in your case that's 9.3 ppm and should never let the chlorine drop below the minimum of 7.5% of the CYA level or 6.1 ppm. Your current FC is below that which is why you now have algae. You also have Combined Chlorine (CC) = 5.0 - 3.7 = 1.3 ppm. You will need to seriously shock your pool with chlorine, but since your CYA is high it will take a huge amount of chlorine so rather than go that route I suggest you just mini-shock by adding 20 cups of 6% unscented bleach (Clorox Regular or off-brand Ultra) or 10 cups of 12.5% chlorinating liquid. This will raise the FC by about 10 ppm.
I wouldn't try to completely battle your algae with your high CYA level. So I suggest you add the chlorine to get the FC level up higher just to prevent the algae from growing as quickly and start draining and refilling your pool by half its water volume so you get your CYA level down to around 40 ppm. You can use a continuous drain/refill method to avoid risk of the sides coming in or you can do multiple drain/refill to a little below the skimmer line (pump needs to be off in that case). This will dilute all your chemicals, not just CYA, but you'll have a much easier-to-maintain pool afterwards. When adding chlorine (bleach or chlorinating liquid) do so VERY slowly over a return and to be extra safe, you can predilute it in a bucket of pool water (say, 2 cups of chlorine in a 2+ gallon bucket, then add that slowly, repeat). This is just being extra cautious -- for Cal-Hypo you would always pre-dilute, but for chlorine pouring very, very slowly is usually OK, but most people become impatient so using pre-dilution kind of forces one to slow things down.
You should immediately order yourself a good test kit. The Taylor K-2006 from Taylor here or from Leslie's here or the even better TF-100 kit from tftestkits here. Your pool store's numbers sound reasonable, but you should really test these things yourself to be sure and its the only way to know how much chlorine you really have since standard kits (OTO and DPD) only test up to 5 ppm while the FAS-DPD chlorine test you will be getting can test very accurately and up to 50 ppm FC so it's good for testing when shocking with chlorine.
By the way, I can assure you that your pool does not have 0 TDS. But that number isn't important.
What was your source of chlorine you were using? Your CYA level got high so I suspect you used Trichlor tabs/pucks or Dichlor powder/granules at some point, is that right? You should instead use a source of chorine that does not have CYA in it -- that is, unstabilized chlorine such as bleach, chlorinating liquid, Cal-Hypo or lithium hypochlorite. Cal-Hypo also increases calcium hardness, but is probably OK for a while since your CH was low, but must be pre-dissolves before adding. Lithium hypochlorite dissolves very quickly but is very expensive. So bleach or chlorinating liquid are your best bet but you must add them very slowly and mix in the pool thoroughly, especially with an above-ground pool since without a floor drain circulation can be quite poor and you don't want the chlorine to settle at the bottom of the pool (it won't if mixed well, but it may if you dump it in too quickly).
Richard
-
TF-100 is only available on line here, but they ship quickly and I think it's worth it. The Taylor K-2006 will likely not be available in any pool store though the K-2005 might be, but do NOT get that. If you can't find the Taylor K-2006 in a store, then you can buy it online directly from Taylor here or from Leslie's here. But if you end up having to go online, you might as well get the TF-100 since it's more economical. It has a more logical size to the amount of reagents, can measure CYA down to 20 ppm (K-2006 only measures down to 30) and comes with both the accurate FAS-DPD chlorine test as well as a quick and dirty OTO test for quick checks. And no, I have nothing to do with that test kit -- I just think they've done a good job. It's just some folks who are pool users associated with the TroubleFreePools forum. You can also get lots of help there as well -- I look at and respond to multiple forums, but that's the main one along with The Pool Forum, but there are no new registrations on The Pool Forum.
There isn't a rush. Take a deep breath and relax. Your pool is not in bad shape -- it just needs a little tweaking. Order the TF-100 test kit online, wait a few days, then report back. And yes, you'll have to keep adding acid, but you're not adding as much as you used to and we'll take care of that soon. I think turning off your water aeration features (waterfall and bubbler) will help (you can let me know if it does).
Richard
-
I am sorry to say, the test kit you have is not good enough. You really need to accurately test your CYA level and the test strips won't do that. Also, the test kit you have for chlorine is probably a DPD test where you look at the intensity of red color (or it could be OTO where you look at the intensity of yellow color). These will not measure chlorine levels above 5 ppm so are no good to know if shock levels of chlorine are maintained (there is a "dilution" method to test high chlorine levels, but it's not accurate). So I still suggest you get one of the better test kits I mentioned. The chlorine test in those better kits is called FAS-DPD where after adding powder to turn the sample pink, you simply count drops until the sample turns clear -- then multiply by 0.5 or 0.2 depending on sample size and you've got an accurate Free Chlorine reading AND you can then add another reagent, turn pink again, count more drops and get an accurate Combined Chlorine reading. You'll also get accurate tests for Calcium Hardness (CH) and Cyanuric Acid (CYA) that should be better than your test strips, and yes you'll get similar tests for pH and Total Alkalinity (TA), though even the pH test might be better (Taylor, which also makes the reagents in the TF-100, uses a better reagent for pH tests that avoids some chlorine interference).
I would feel really bad if we added CYA only to find out that it was already high and that the test strips gave us a false low reading. If you want to do some of the other things in the meantime, like lowering the TA even more, we can do that, but given your direct sunlight in southern Texas, I really think the higher CYA level will help -- I just don't want to go too far.
As for lowering SWG production, yes I mean lowering the 80%, but you can't do that yet -- this is what we want to be able to achieve through the higher CYA levels (and maybe adding Borates) to lower chlorine consumption. With lower chlorine consumption, you can lower the SWG chlorine production (i.e. it's output or percentage on the Intellichlor). So don't change that yet -- I was just preparing you for what we hope to do IF with higher CYA you find that the chlorine level rises well above 3 ppm.
Since you already have stabilizer, we can use that first. I mentioned the Dichlor because it dissolves much more easily than CYA, but I forgot you said you already had stabilizer. After we measure the accurate CYA number, then we will add your stabilizer by putting it into a sock or panty hose and putting it over a return -- CYA takes a long time to dissolve unless you have lots of water flow over it. With this technique it should dissolve in a day or two instead of taking a week. You might have to hook up a pool pool to dangle over the edge or something like that to hold the sock/panty hose in place.
If you use the CYA you have, then you wouldn't use the Dichlor for shocking. Instead, you would get either unscented bleach or chlorinating liquid to do the shocking. Except for the peak point of shocking (and we'll do that at night and see what the levels are the next morning), you can swim in the pool during most of these additions, waiting at least a little bit -- 15 minutes or so -- for some dilution. We won't be adding very many chemicals, but this depends on your accurate numbers. I believe your Calcium Hardness (CH) is too low since you said you had a PebbleTec pool and that requires calcium just like a plaster/gunite pool -- so yours is way too low. You will need to buy Calcium Chloride which is in products that say things like Calcium Increaser. As for how much, that depends on the accurate CH reading and we don't have that because you are using test strips for that. Again, get a proper test kit FIRST before we do anything else. There is no rush in this. You'll get the test kit from tftestkits.com within days.
If you know there will be a day when your kids won't be using the pool, then the previous night would be a good time to do the shocking. If I assume the CYA is around 40 ppm, then we would shock to 16 ppm FC which going from 2 ppm FC in your 13,000 gallon pool would take about 3 gallons of Clorox Regular unscented bleach (it says 6% Sodium hypochlorite in the ingredients and also says 5.7% Available Chlorine) or you can use an off-brand unscented Ultra bleach if it's a lot cheaper, but it may not be guaranteed to be as potent (i.e. 6%).
Richard
-
Sorry to make you dizzy.
Your use of test strips explains some of the TA variability. Test strips are not accurate with a few exceptions (test strips for Borates and for Salt are generally accurate -- both from AquaChek). Your TA has actually been dropping, just as predicted. Notice also how the total amount of acid needed has been dropping with the lower TA -- that is a good thing. So the first thing I would do is get yourself a good test kit, the Taylor K-2006 from Taylor here or from Leslie's here or the even better TF-100 test kit from tftestkits here. It's much easier to maintain a pool and solve problems when you have accurate information. You will even do a better job than most pool stores!By the way, if you have any water aeration features, such as waterfalls, spillovers, fountains, etc., see if you can turn them off and see if that makes any difference in preventing the pH from rising. Also, if you have a pool cover, then use it and see if that helps (sometimes it does, sometimes it doesn't -- it depends on whether those bubbles escape from the return into the air or stay under the cover).
I suspect that your kids are complaining because the pH is getting high. A pH of 7.5 is closest to human tears and up to 7.7 is still OK but above that (or low pH below 7.3) may start to sting the eyes.
The main thing you want to try and do is to lower your SWG production, but you can't do that unless you lower your chlorine usage. I do suggest raising your CYA level -- first raise it to 60 ppm and we'll see how that goes (we may end up going to 80 ppm eventually, but no higher than that). You will also need to target 3 ppm as your Free Chlorine level, but to accurately test that you really have to get one of the test kits I referred to above -- the strips just aren't good enough (even the standard color tests for chlorine aren't good enough). So get the test kit first since we need to accurately know what your current CYA level so we know to add the correct amount (which we will likely add by using Dichlor, which is chlorine and CYA, rather than just adding CYA alone -- that way we can shock your pool as well). So the following is what we will plan to do, but start by getting the test kit. Do not do the other steps until you report your full set of numbers -- I will then be able to tell you exactly how much you have to add of each chemical.
1) Get a good test kit.
2) Add CYA and also shock the pool by adding Dichlor powder/granules to get the CYA to 60 ppm. Once the CYA level is reached, we may continue to shock the pool with bleach or chlorinating liquid until we're sure there is no unusual chlorine consumption (FC holds overnight and no measured CC).
3) Target a 3 ppm Free Chlorine (FC) level -- see if you can lower your SWG on-time (output level) to do this (because the CYA should cut down chlorine usage; if so, then the pH should rise more slowly)
4) Lower the TA level even lower using a low pH and aeration with acid procedure (I'll describe that more later if we get to this)
5) Add 30-50 ppm Borates to the pool both as an algaecide and as an additional pH buffer
We may not need to do all of the above -- we'll see if the first few steps help enough. The good news is that once your pH becomes more stable, maintenance will be much easier. You will still likely have to add acid to your pool once in a while, but it won't have to be nearly as frequently -- hopefully we can get the test and acid down to just once a week or even less.
In addition to the full set of tests from the test kit, with Free Chlorine (FC), Combined Chlorine (CC), pH, Total Alkalinity (TA), Cyanuric Acid (CYA) and Calcium Hardness (CH), I also need to know the size of your pool in gallons (if you know it; otherwise, the shape and width/length or diameter and average depth) and whether it's a vinyl or plaster/gunite pool and the kind of filter you have (cartridge, sand, or DE).
Don't worry, your problem will be solved soon and I'm sorry I overwhelmed you with technical detail. I'll try and focus just on solving the problem, not explaining how it works.
Richard
-
It is very common for SWG pools to have a strong tendency to rise in pH. Though you'll hear some pool people say it's due to the chlorine generated by the SWG being basic/alkaline, that really isn't true since the initial addition of chlorine makes the pH rise, but chlorine usage makes it drop and these cancel each other out. The real reason for the pH rise is that the SWG doesn't just produce chlorine, but also produces tiny hydrogen gas bubbles (you can readily see these if you turn on the pump and SWG at night with a pool light where you'll see lots of tiny bubbles coming out of the returns). These bubbles aerate the water pulling carbon dioxide out of the pool and into the air. Pools are intentionally over-carbonated, like a tasty carbonated beverage, though obviously not nearly as carbonated. This is what TA is (mostly) -- carbonates in the pool. This excess of carbon dioxide in the pool gets outgassed into the air and this process causes the pH to rise with no change in TA.
So, when you then add acid, you lower both pH and TA. So over time, the TA will drop (but that's not what you are seeing so I'll talk about that in a bit). The pH goes up, you add acid which has pH and TA go down, pH goes up again, etc. with the long-term result being a lowering of TA. The rate of outgassing of carbon dioxide is faster when the pH is low, the TA is high, and there is more aeration.
Now what does not make sense in your situation, relative to what I just described, is that you describe not only a rise in pH, but a tendency to rise in TA as well. You say that the TA is now 90, but will rise until it hangs out at 150? If you are measuring both when the pH is the same each time, then the only way this can happen is if carbonates are being added to the water. You aren't adding any pH Up (sodium carbonate) or Alkalinity Up (sodium bicarbonate) to the pool, are you? What other products are you adding to your pool? Perhaps one of them has carbonates in them -- I can look them up if they have a Material Safety Data Sheet (MSDS) online or you can look at the ingredients on the bottles.
Anyway, the way to lower the pH rise is ironically to have a low TA. Another thing you can do if your pool is in direct sunlight all day is to raise the CYA level higher to 70-80 ppm and also raise the FC level to 3-3.5 ppm. The other thing that can be done is to add 30-50 ppm Borates (that is adding 20 Mule Team Borax plus Muriatic Acid) which is an additional pH buffer and is also an algaecide. If your chlorine is fighting algae, then the borates will help and allow you to turn down your SWG runtime which will reduce aeration and outgassing and pH rise; same thing is true for the higher CYA level which protects the chlorine from breakdown from sunlight. But for now, let's find out what's getting added to your pool to have the TA rise (we know why the pH rises). By the way, what I'm proposing with the Borates is the same thing as what is done with BioGuard Proteam Supreme (which is essentially Borax with less water "hydrate crystal" content).
Richard
-
The 9600 CT (chlorine in ppm times time in minutes) number is with chlorine and ZERO CYA. You don't have any hope of killing Crypto by chlorine alone in a pool with CYA in it. At 30 ppm CYA, there is roughly 1/30th the amount of disinfecting chlorine as in a pool with the same FC and no CYA. Only when the FC level gets close to the CYA level do you get reasonably high levels of disinfecting chlorine.
You have to raise the FC level to about 16 ppm at 30 ppm CYA (a little more than 50% of the CYA level) to get the equivalent of 1 ppm FC with no CYA at a pH of 7.5 (so you need to lower the pH first before increasing the FC to get the same effect).
The good news is that in a residential pool, Crypto and Giardia are very unusual unless you throw large pool parties with sick individuals. It's more common in commercial pools due to the larger number of bathers and fewer controls of who gets to swim. In many commercial pools, additional methods are used to deal with Crypto and Giardia (such as chlorine dioxide, ozone, and UV).
As for urine, you don't have to worry about that nearly as much as fecal accidents. Urine is relatively "clean". Yes, the urea is an ammonia-like compound, but you don't generally introduce bacteria, viruses or protozoan cysts via urine (or via sweat either). Urea doesn't actually form combined chlorine measured in a CC test. Instead, chlorine slowly oxidizes it forming transient chloramines, but this process might be sped up by sunlight (not sure about that since no CCs are measured).
Richard
-
I have another quick question. I am looking at a TF100 kit and a K2006. The K2006 is a few bucks cheaper but not significant. They look like they perform the sames tests. Does anybody have input about which one they like?
The TF100 is a better value because it contains more logical volumes of reagents (such as for the CYA test). With the K-2006, you'll end up ordering more reagents in an unusual order. I still have my K-2006, but will likely switch over as I run out of reagents. As for differences in tests, the TF100 has an OTO test in addition to the FAS-DPD test for chlorine (so you can do quick tests with OTO when accuracy isn't needed) and the K-2006 has acid/base demand reagents that hardly anyone uses since they are not sensitive enough (I sometimes use them to force the pH colors to move one way or the other if I'm not sure of the color). Also, the CYA test in the TF100 measures down to 20 ppm while the K-2006 only measures down to 30 ppm.
Either way, you won't go wrong and the reagents are interchangeable between the two kits.
Richard
-
The hockey puck of chlorine was probably a 3" Trichlor tab and if it were 8 ounces, then one tab usually lasts around 4 days or so in a floating feeder so would add 43 ppm FC per day which is way too much and would also add 26 ppm CYA per day. It would also make the water very acidic.
Though the high chlorine is not good, the acidity is worse unless he compensated by adding Spa Up regularly. I suspect he didn't. The damage from high chlorine and especially from acidic conditions would be in the metal components in the pump. I'd say he was very lucky and if something happens to the equipment when you use this tub, you'll know why it failed.
Why Don't People Use Pool Chemicals In Spas
in Hot Tub Water Chemistry
Posted
You are right. I forgot about that. However, you don't need to saturate the water with calcium carbonate so don't need Calcium Hardness (CH) to be near 300. I believe waterbear found that a CH of somewhere around 100-150 works well to reduce the foaming. Again, thanks for reminding me about the need for at least some calcium.