CYA Testing and Depletion

[Sherra]

No, the sun does not deplete CYA. The only way to lower is drain/fill or let your pool turn into a swamp over the winter...and even for some people the swamp thing doesn't change their CYA levels...CYA is a strange creature...

Oh, there is a chemical you can add to reduce the CYA, but it's very expensive and it takes a lot to do it...it's way cheaper to drain/fill.

[CUTURHAIR]

Luckily, my pool's cya drops over the winter and the pool is crystal clear and not nasty. I haven't "closed/winterized" my pool for the last 2 winters and luckily, have not had any problems, knock on wood. However, I have been battling a very small amt of mustard algae this season for the first time, but my CYA seems to go to zero over the winter every year, whether I open to a clear pool, or keep it open and clear all year. I had it tested for nitrates which I believe Ben said could cause that drop, but there were no nitrates, according to the pool store. I believe that test was sent out for testing, and not done at the store, but that was a good few years ago.
John

[CarlD]

OK, let's clear up a misconception:
You CAN dump half the water in your vinyl pool safely. You just need to make sure there's at least 1 foot of water in the shallowest area, then refill. You don't need the Poconos Plastic Sheet method for that.

A CYA of 50ppm is the high end of normal, but still normal--and a good number for a VERY hot,sunny area and lots of usage. That's where you get to if your CYA is 100 and you replace half your water.

Hope that helps.