Very High CYA - 130


Active member
Jun 23, 2007
Hi. This is my first post. I got a taylor test kit yesterday and measured my CYA level at 130. I just had my pool water tested a couple of days ago at a pool supply store and they didn't say anything about it! I also have mustard algae that's been impossible to get rid of. The pool store gave me some copper based algecide to get rid of it, but after reading posts on this forum, there's no way I'm using it.

My question is, how do I get my CYA level down to a reasonable level? I want to tackle that problem before I try getting rid of the mustard algae.

I've been using tablets or pucks for the last two years and shocking only about once a month. I guess that explains the high CYA. I shocked my pool a week ago, but the chlorine level hasn't gone down.

Here's some info about my pool:

20,000 gallons vinyl pool
Calcium Hardness=220


Mod Squad
TFP Expert
Platinum Supporter
LifeTime Supporter
In The Industry
Apr 1, 2007
Sebring, Florida
Probably the only practical way is to do a partial drain and refill. Draining 50% of your pool and refiiling would get you down to a manageable level but cost 10k of water.

If you don't like that approach, normal refills and a winter exposure to rain and low chlorine levels seems to make a significant reduction for many, but not all, pools.

PS - other than CYA, your other numbers are fine. You might try to get the Alk down to around 90-120 but 160 is not alarming.