Over stabilized


New member
Jun 1, 2019
Hello, I moved into a new house with a pool. I have never owned a pool before. The pool is inground plaster 29,500 gal.
I have purchased the TF 100 test kit. I have been testing and found my CYA out of range high. It looks like the previous owner was using dichlor shock and chlorine pucks. So I'm thinking that is the reason for the high CYA. From what I have read, if i want to lower my CYA i will have to drain some water from the pool and refill. This really will be difficult, my water source is a well it seems like it will take forever to fill the pool after lowering, and possibly run the well dry. I guess I can get water delivered. Is there any other way to lower CYA?
Thanks for any help.


TFP Expert
LifeTime Supporter
Jan 6, 2010
San Dimas, CA (LA County)
What is your CYA level? "out of range high" tells us nothing. Is it 120 or 300? It makes a big difference. You can repeat the test using the dilution method in Step 8 here.

If your pool isn't green or cloudy, you can maintain it with high CYA. I've done it. I was in exactly the same position -- previous owner and his pool guy used pucks. You're on a well. I was under restrictions that could have led to a hefty fine and a restrictor being placed on my meter at my expense. So I lived with it for a season. It isn't easy and I don't recommend it if it can be avoided, but I will attest that it can be done.

What I started with was emptying my spa into my pool and then pumping water out of the pool to water the lawn while I refilled the spa. An inch or two at a time, when the pool's average depth is 60," can make a discernible difference over a few weeks.

I also set up one of my raingutter downpouts to feed the spa. It acts as a settling basin. You get rain in the summer in Virginia, don't you? I had to wait until Fall! Capture what you can.

Your pH test will always be iffy above 10 FC, but if you add the drops and do a quick inversion to mix, you'll get a close reading. After a few seconds it will react with the high FC and read wrong.

If you have algae, you're kind of spiral-fastenered.

There was -- maybe still is -- a product called bio-active that was supposed to neutralize CYA. It wasn't very successful. If you're the lucky sort who wins raffles and lotteries, it might be worth a gamble. If you're just average, save your money.