Phosphates Masking CYA Readings??

[Poolsean]

Most reagent cya test kits don't start measuring the CYA until about 30 ppm, up to 100 ppm. Of course, if you're at 0 ppm, the water would be crystal clear with the cya reagent added.
Assuming that you're at 0 ppm, or even 10 ppm, 1 lb raises 5,000 gallons 25 ppm. How large is your pool?
I agree with Janet on the phosphate issue. Not much to worry about unless you have algae growth somewhere.

[waterbear]

I also agree with Janet and Poolsean. Unless you have continued algae blooms that you cannot get under control don't worry about the phosphates. My own pool has had phospahte readings between 2000-3000 ppb and I have never had a green pool because of it.

[squirrel49]

Our pool is ~24,000 gallons, 6 lbs should have raised the CYA about 30ppm. I know the CYA is in the pool and it is my understanding that the only way to lower or remove it is to drain the water. The pool store read 0 ppm on 3 separate water samples weeks apart, once before and twice after I had added the stabilizer. They claim that my extremely high phosphates are masking the CYA test. Is this possible?

I plan on having another pool store test my water for CYA. I would be testing myself as I usually do but I am out of the CYA regent.

[waterbear]

I test a lot of water and have never seen or heard of phosphates masking a CYA test. I have experienced a temporary lowering of CYA when a lanthenum based phosphate remover is added to the pool in a large dose but it has not happened every time and the CYA results have returned to normal in a week or two. I have never seen this particular effect documented anywhere but it is something I have noticed in my testing and also in my own pool when I was experimenting with lanthenum based phosphate removers.

[squirrel49]

Well,

Had my water tested at another store. Measured 35ppm CYA (Which makes sense based on the previously added 6lbs stabilizer) and ~1000 ppb phosphates. They never heard of phosphates masking a CYA test either. Looks like the first store was full of B.S.

All I plan on doing now is adding another 6lbs stabilizer and enjoying the summer. Am not planning on doing anything else about the phosphates.

Pat.