I am having trouble maintaining stabilizer levels in my pool. My pool was fill at the end of October, and to the best of my knowledge 3 lbs of CYA was added at that time. Pool volume is 7500 gallons.
Pool store testing results:
11/10/2007 60 ppm
11/24/2007 50 ppm
12/08/2007 45 ppm (1.5 lbs of CYA was added)
12/21/2007 45 ppm (again added 1.5 lbs CYA)
Test results using ColorQ:
12/18/2007 29 ppm
12/22/2007 46 ppm (at 2 pm)
12/22/2007 36 ppm (at 5 pm)
I also am testing with HTH 6-way test strips which have blocks for 0, 30~50, 100, 150 and 300. All tests match the 30-50 block.
According the the Pool Calculator website, the initial 3 lbs of CYA should have given a level of 48 ppm. The two following additions of CYA should have added 24 ppm each for a total level of 96 ppm. There does not appear to be a leak in the pool, I fill it about two inches once a week. Allowing for 10 to 15 % splash out over the two months, the level should be 86 ppm.
I know the readings can vary between testing systems, but tests within a given system should not vary that much. This leaves two options: There is something interfering with the CYA test, or something is destroying the CYA.