Zero CYA in an indoor pool - chicago winter

[ckf]

I was looking up something else on TFP and came across a comment on CYA - that CYA should never be zero even in an indoor pool b/c having any FC over 2 can be irritating to the skin, eyes etc b/c without CYA it makes the FC harsher or something like that . . . is that true? I did look up the CYA/CL table in Pool School but it doesn't really specify indoor or outdoor and up until now what I have read about CYA was that it stabilized the FC which - when I finally got our pool balanced - I have not had a problem with.

I thought CYA stabilized the FC especially in an outdoor pool when exposed to the sun. But I thought in an indoor pool having a CYA reading of <20 or zero was not a big deal b/c the FC would not burn off as fast anyway b/c of the lack of sun exposure. I have not had trouble keeping my FC levels around 2 to 4, but again in another posting it said that 2 to 4 in an indoor pool without CYA can be harmful to the swimmer . . . is that true? The other post on TFP also said that an indoor pool without CYA should have an FC reading of 0.2 . . . again is that true?
Also, does CYA change with climate? We are in the middle of a Chicago winter, will that lower the CYA or increase it?

I am only concerned b/c my son who is 3 swims in that pool and I didn't realize that having no CYA would be harmful to him. We have never had a problem with him having a reaction in our home pool. I'm feeling a little panicked b/c here i thought I finally got our pool to where it should be and I wasn't worried about the CYA b/c it was indoors and now I have to worry about the CYA. Have I been harming my son? Please help!

 

[chem geek]

It's not harmful in an immediate sense and many states have regulations prohibiting the use of CYA in commercial/public indoor pools (as well as spas), but having 2 ppm FC with no CYA will have an active chlorine level that is about 20 times higher than the typical outdoor residential pool with an FC that is around 10% of the CYA level. CYA doesn't just protect chlorine from sunlight, but hugely reduces the active chlorine (hypochlorous acid) concentration.

Though the German DIN 19643 standard when using ozone has the FC range be from 0.2 to 0.5 ppm with no CYA, it is very hard to maintain a 0.2 ppm FC level consistently, especially without automated dosing. So I wouldn't try that.

The problem is that with an indoor pool without sunlight you often need some form of supplemental oxidation, be it UV, ozone, or use of non-chlorine shock.

My wife has experienced this difference between an indoor pool with 1-2 ppm FC and no CYA where her swimsuits degrade (elasticity gets shot) after a single winter season and her skin is flakier and hair frizzier while in our own outdoor pool with 3-6 ppm FC and 40 ppm CYA the swimsuits last for years with minimal sign of wear and her skin and hair are not as adversely affected. This is most likely due to the indoor pool having 10-20 times the active chlorine level of our outdoor pool.

If you do decide to use some CYA in the indoor pool, don't overdo it. Use a small amount, say no more than 20 ppm, and then have your FC in the 2-4 ppm range and see how that works for you. If you find a buildup of Combined Chlorine (CC) over time, then you can use non-chlorine shock (MPS) every once in a while to get rid of organics (mostly urea) that aren't dealt with as quickly without exposure to sunlight.

 

[ckf]

What do you suggest I use to increase the CYA?

Before we switched to BBB and before I had any knowledge about pools we were just using the tablets for chlorine and when I found TFP and tested for CYA I found that it was off the charts - I can't remember what it was but we had to empty almost the entire pool to get the CYA down.

So, I am a little nervous about using the tables. Is a liquid stabilizer any more precise when it comes to increasing CYA? The pool calculator says to add 69 oz of liquid stabilizer to get the CYA up to 20. I know everyone says that liquid stabilizer is very expensive, but if it is more exact on raising the CYA than I'd rather use that than guess with the tabs.

What do you think?

Thanks,
Cissy

 

[frustratedpoolmom]

It is not more precise than granule - there is little reason to pay extra for the liquid. You can purchase the granule at pool stores, or big box stores with pool departments...look for "Cyanuric Acid" on the label and you want something that is at least 90% CYA. American Sale was selling a mixture that was only 50% CYA a couple of years ago so check the label. You can use the Pool Calc to measure the CYA granules as precisely as the liquid. Pour it into your skimmer, and then do not clean your filter for at least a week.

 

[chem geek]

You could use Dichlor as your chlorine source for a while since for every 10 ppm FC added by Dichlor, it will increase CYA by 9 ppm. It's reasonably economical since you get both chlorine and CYA at the same time and it dissolves a heck of a lot faster than pure CYA. Of course, you won't get your CYA up immediately, but that's probably better anyway since you can see how things are going. Just stop when you've cumulatively added 22 ppm FC which should be around 20 ppm CYA. You can use The Pool Calculator to calculate dosages for FC using Dichlor. Dichlor comes in smaller sizes since it's also used in spas so you won't have to have a lot leftover.

 

[ckf]

Great! Thanks for all the advice everyone.