Phosphates Masking CYA Readings??

I ran out of the CYA Reagent for testing CYA levels, so I went to the pool store to have my water tested. They said I had less than 10ppm CYA, so I purchased 6 lbs of stabilizer, added it, and had the water re-tested 3 days later. This time, they said my CYA level was 0! I knew this to be incorrect since I had just added 6 lbs stabilizer. They then tested for phospates which measured off the charts at > 5000ppb. They told me that a high level of phosphates could mask the CYA readings. Is this true?

I added two quarts of SeaKlear Phosphate Remover, and had the water re-tested. The phosphate now read ~4000 ppb and the CYA still read 0. They told me that phosphates are usually due to fertilzer, etc... I found this hard to believe since I never get fertilizer near the pool and have not ever had this problem in the past.

I then think I found the source of my phosphates. Earlier in the season, while trying to correct what I thought was a staining problem, I added a sequestering agent (GLB SequaSol). It turns out that this sequestering agent is phosphate based. I am now convinced that this is the cause of my high phosphate level.

A few Questions:
1) Do I need to continue to try to lower the phosphate level from the 4000ppb it is at now?
2) Does a very high phosphate level such as mine mask the ability to accurately read or detect CYA levels?
3) If not, why can't they detect any CYA even after adding 6 lbs of stabilzer (Cyanuric Acid)

My other readings are as follows:

FC 2
CC 0
TC 2
PH 7.6
ALK 90
CAL 220
SALT 3400
CYA 0

Unless you're having an algae problem that absolutely cannot be killed, I would not worry about phosphates--they are the latest and greatest way to separate you from your money by convincing you to add something to your water that you don't really need. As for the CYA not showing up, you didn't say whether you broadcasted it or put it in the skimmer, but it generally takes a week or so before it dissolves enough to show a testable level.

Janet

Its been two weeks since I've added the cyanuric acid. I added it in two nylon stockings, one in each skimmer.

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.

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.

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.

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.

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.