CYA in indoor pools?

Hi there,

I am the owner of a relatively small, indoor commercial pool. Our pool is 25ft. x 50ft. We keep the pool at 92 degrees. Our pH is at 7.4 and our FC is at 1.5. Our CC is roughly .5. We do have a high bather load (approximately 120 people per day.) Recently, some people have mentioned that the pool is causing them itching/irritation after prolonged exposure to the water. I am wondering about adding a small amount, say 20 ppm of CYA to the pool to help act as a buffer on our active chlorine. When the pool was first built, the contractor and the guy who installed the equipment said don't use CYA. A CPO instructor also said don't use CYA. Also, what I have read online mostly says don't use CYA indoors. This seems to be because the CYA is mostly intended to shield the chlorine from UV rays, which are not present in indoor pools. However, on a different forum, several people indicated that it would be okay to use a small amount of CYA in order to lower the active chlorine, thus preventing the irritation/itching that some bathers have mentioned.

Does anyone have any info regarding the use of CYA in indoor pools?

CYA also significantly moderates chlorine's strength. This question was also asked in this forum and this forum.

A CC of 0.5ppm is very likely the cause of irritation complaints. You would need to raise, not reduce, the free chlorine level if you were to introduce CYA as CYA inhibits chlorine's sanitizing action.

Most of the members here have experience only with their own private outdoor pools. PoolDoc prefers to handle commercial pool questions himself, I'd wait for his opinion.

If I remember correctly, PoolDoc has always been VERY leery of any CYA in an indoor pool. I think it has to do with fumes--but don't quote me on that. Plus, UV breakdown is not an issue indoors.

No, it's not fumes since there is LESS chlorine evaporation when the active chlorine level is lower. When you don't use any CYA at all, then the active chlorine level is higher unless you maintain a quite low FC level. That's what DIN 19643 does in Europe -- it specifies a 0.3 to 0.6 ppm FC level with no CYA (0.2 to 0.5 ppm FC if ozone is used) but that's not the minimum in the U.S. where it's usually 1 ppm FC minimum in most states and in some places it's higher. For a high bather-load pool, you need a higher FC to not run out locally unless you have outstanding circulation. With CYA, it acts as a chlorine buffer so can hold chlorine to be released anywhere in the pool quickly.

The only downside to having a small amount of CYA indoors is that the lower active chlorine level means slower oxidation rates so it really becomes important to use supplemental oxidation system, but the plus is that this will lessen chlorinated disinfection by-products.

Specifically PoolDoc says the following about CYA use in indoor pools in this link:

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And, you don't need to stabilize indoor pools: there's no sun inside (well, hardly any). Actually, there may be a reason to use small amounts of stabilizer on some indoor pools, but I'm still testing this. If you are having operational problems on an heavily loaded indoor pool -- residential or commercial -- and are ALREADY following the other recommendations on this page, contact me.

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and in this link he says the following:

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Well, why not just run LOW chlorine levels without stabilizer?
On indoor pools, with no exposure to sunlight, that's definitely an option.

But on outdoor pools, chlorine's half-life without stabilizer can be as little as 30 minutes under full so. This means that if you have 1 ppm at noon, you'll have 0.5 ppm at 12:30 and 0.25 ppm. To keep a pool safe under those conditions means that you have (1) add chlorine continuously, and (2) have a really good circulation system that is running 24/7.

It also turns out you have to be willing to use a lot more chlorine than you would otherwise.

So stabilizer is necessary for good sanitation?
Yep.

Without stabilizer, everything has to be pretty much perfect in order to maintain a santized and algae free pool. Years ago, commercial pool were operated with chlorine gas, soda ash, and not much more. There were a lot of cloudy, stinky public pools!

Swimming pools are enough work, even when done right. The BBB Method is ALL about not making it worse by adding stuff you don't need.

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In this link he says the following, but that's mostly referring to higher CYA levels typical of using Trichlor indoors, not low levels such as 4 ppm FC with 20 ppm CYA:

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Stabilizer (on indoor pools) -
Stabilizer (conditioner, cyanuric acid, isocyanuric acid) is only useful if your pool is exposed to sunlight. Indoors, it does nothing for you, and can make things much worse.

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Originally Posted by poollady

I am the owner of a relatively small, indoor commercial pool. Our pool is 25ft. x 50ft. We keep the pool at 92 degrees. Our pH is at 7.4 and our FC is at 1.5. Our CC is roughly .5. We do have a high bather load (approximately 120 people per day.) Recently, some people have mentioned that the pool is causing them itching/irritation after prolonged exposure to the water.

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I serviced a fitness center pool with conditions almost identical to yours for over 10 years . . . and my wife taught water aerobics in that same pool. Briefly, there is no simple or complete answer. Hot indoor pools with high bather loads *will* have the problems you describe. You can reduce, but not eliminate them.

Here are possible steps:

1. Install a commercial UV system. This will INCREASE your chlorine consumption, but will partially replicate the high-intensity oxidation that occurs on outdoor pools from the combination of chlorine + sunlight. The improvement in water quality will be very significant . . . if you get a large enough UV system.

2. Make sure that your ventilation system is on 10% or more outside air. Outside air makes it harder to maintain stable room air temperatures, so service techs tend to shut it off. BUT, without outside air real problems with air quality WILL result.

3. Keep all classes to 1 hour or less, and empty the pool for 5 minutes between classes. The reason is simple: to make people go pee! Urine and chlorine react very badly together. Sunlight + chlorine (or UV + chlorine) can break down some of the chemicals that form, and good ventilation can remove others. BUT preventing the formation of those chemicals is best. I once fixed a SEVERE problem on the pool I serviced by persuading the manager to cut a mom + young child swim class from 70 minutes to 50 minutes AND by having the instructor CONSTANTLY remind the parents to potty all children BEFORE they entered the pool.

IF YOU CAN ELIMINATE PEE AND LOTION FROM THE POOL, YOU WILL GREATLY REDUCE THE PROBLEM!

4. Try to keep people with incontinence problems (urinary & fecal) out of the pool. Fecal incontinence poses an IMMEDIATE health risk to other swimmers; chlorine does NOT instantly sanitize small fecal particles. Urinary incontinence leads to the pee+chlorine issue mentioned above. This means -- ideally -- that both toddlers AND the "Depends" set should be excluded. At a minimum, try to exclude those who are fecally incontinent (young and old) and insist that others put on a fresh diaper before entering. Encourage everyone -- young and old -- to PEE FIRST!

5. Your regulars will tend to adapt by putting lotion on before they enter the pool. Do all you can to discourage this; the lotion makes the problem worse. Ask people to rinse any lotion off first, and then suggest that they shower and put on lotion after.

(If you sell massage therapy, it may be possible to suggest that the therapist apply J & J Baby Oil Gel at the end of the massage. During the years my wife worked as an instructor, I routinely put this gel on her entire body, from neck down, AFTER showering. We kept a soft towel in the bathroom for wiping off excess. She found the Aloe + Vit E gel - pictured below -- worked best. The areas that itched worse on her, and her students, were back and lower legs. Pool user can self apply the gel to legs, but will need help to get it on their back. CAUTION: you do NOT want this stuff in the pool!!)

6. Maintain your chlorine and pH the highest allowed levels. On my pool, the problem was least bad with Cl= 5 - 10 ppm and pH = 7.8 - 8.0. I usually had 5 - 10 ppm CYA in the pool as well.

7. Turn the temperature down. You can find plenty of literature suggesting it's UNSAFE to exercise or swim at 92 degrees. People pee and sweat less at lower temperatures. Unfortunately, your older chit-chat / non-exercising women will raise unholy he## when you do so. But, if anyone is doing anything other than standing around, you really shouldn't have the pool above 90 -- it does stress old hearts!

8. Make sure your filter is (a) in great condition and (b) oversized. DE is best, an oversize sand filter is effective and easiest to maintain. Cartridges are a disaster in an application like yours.

9. Institute a regular water replacement program -- something like 20% drain and replace monthly, and complete drain and refill annually.

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