Still Confused About CYA

I have pretty high CYA (>120). Reading other threads concerning testing and adjusting pool chemistry, I learned that the only way to get rid of CYA was to drain and replace - I thought. Then I read Ben's sticky at the top of this forum and learned that bacteria can also get rid of CYA (biodegradation).

So ... the good news is that bacteria could eat all my CYA. The bad news is they (the bacteria) end up defecating in my pool. One way or the other, if I want to lower my CYA I'm going to have to drain. This is such an issue for me because I have an IG vinyl pool.

Am I understanding all this correctly?

-Jim

Hi, Jim,

Yep, your understanding is correct.

However, there are two ways you can safely drain your pool.

1. Drain 50% and refill. If your CYA is still high, drain 50% and refill again. That should do it. You could do it again if you wanted but that'll probably get you in a range you like.

2. Find a plastic sheet wider and longer on both sides than the depth of your pool. Spread it across the pool and start filling into the top of the sheet while simultaneously draining from under the sheet. Theoretically, you could do almost a 100% drain safely.

Thanks, Dave. I plan to try the plastic sheet method next spring and I'm glad to see an endorsement of the technique. I'll be posting my experience with the process next year.

-Jim

Well, I tried a search about CYA and got nowhere (too common or too short, even for just titles) so I just have to ask -- what is it and why would it get so high?

My own CYA is 60 for our 15,000 IG concrete pool, and it worries me because I see the "normal" range is between 30-50. Is there something in particular I should do *now* in order to keep it from going higher?

Yes, immediately stop using stabilized chlorine. Pucks, sticks, granular dichlor are all stabilized and they are adding CYA to your pool constantly. Bleach adds nothing but chlorine. Your CYA is plenty high right now.....that's why I used "immediately":)

There are a bunch of threads on this forum that explain CYA. Read the stickies at the top of each forum.