Phosphates Masking CYA Readings??

[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.