Just took over from pool guy and CYA is 170


New member
Jul 13, 2020
Chandler, AZ

Live in Phoenix area, with a 20k gallon pool. I got the Taylor k2006 kit and my CYA level is off the charts at 170 and my CH is 424. I've read I should at least partially drain the pool, but also I dont think I should due to possible damage until temps drop in the fall (I think we are at 10 days straight of 110+ here). I got rid of the chlorine tab floater and have switched to liquid chlorine . But since with CYA conversion tool doesn't go above 100 what should I keep my chlorine level at to avoid a green pool until fall but still be able to swim?

Thanks in advance


Gold Supporter
May 27, 2019
Houston, TX
I don't think you can properly run the pool that high. To get to 40 PPM, you need to drain at least 3/4 of the water. I'd suggest 4/5th, and then measure and add both CYA and Calcium. You will save yourself a lot of frustration. At 170, you need to run a FC of 13+, bare minimum.

I have a 24,500 Gallon pool. I had terrible problems with CYA, maybe 400+ (8+ years of tablets). I tried the drain and refill, but still kept using the tablets. This year I did a complete drain and refill and reset my CYA.

I used two submersible pumps and was able to drain 24,500 in 12 hours. I used my pool fill plus two hoses and I was able to refill in 12 hours. I started a SLAM and had the water clear another 24 hours later.



New member
Jul 13, 2020
Chandler, AZ
Welcome to the forum!
Minimum FC is based on 7.5% of CYA. Target should be about 10-12% of CYA. You will not be able to test pH without a pH meter at those levels.
Read Draining - Further Reading for some ideas.
How did you get a CH result of 424??
I suggest you read ABC's of Pool Water Chemistry.

Thanks for the feedback. I got a CH reading from the pool store that said 424 and then verified it was around that with my kit. I tested pH with my k2006 and it showed 7.6. Is that an inaccurate reading given my CYA level


Mod Squad
TFP Expert
Bronze Supporter
May 3, 2014
Laughlin, NV
pH is not effected by CYA level. FC level above 10 ppm effects the color block pH test.

Do your own CH test. If that low, this water was changed in the last year or so.


Bronze Supporter
Sep 19, 2019
Phoenix Arizona
I did a 50% drain / refill to lower CYA on a house in Phoenix two weeks ago. Its a bit painful but I ran two pumps to drain to 50%. I babysat the pool keeping the pebbletec plaster moist all the time with a spray from his hose. As soon as we hit 50%, threw 3 hoses in and filled while keeping the plaster wet. Worked out well for us but I made sure to keep the plaster wet.

When I took.over our pool, the CYA was almost. 300. Had to drain about 85%.


Well-known member
Aug 31, 2019
Phoenix, AZ
You are right that it's too hot in Phoenix, and if you leave a plaster pool empty in this heat it could cause issues. I think the best thing to do is to drain, and refill at the same time to get fresh water and lower your CYA.

I certainly wouldn't recommend keeping the CYA that high, if you did get an algae problem in this heat you'd have a **** of a time fighting it.

With that said, last summer my CYA was probably above 170, The pool was new to me and I didn't test the CYA properly until the winter where it was 300+.

I was able to get through the summer without an algae problem by keeping my FC above 10ppm (I kept 8 tricolor tabs floating at all times), and by crossing my fingers, but it certainly isn't ideal.