As the title of this thread implies, I've been getting inconsistent CYA test results. I have a test kit with the black dot CYA test. Sometimes I get 30ppm, sometimes closer to 60ppm.
I've been maintaining chlorine levels consistent with CYA=60ppm just to be safe (actually a little higher due to above average sunlight, heat and bather load).
So for CYA=60, minimum FC is 5 and target FC is 7.
If CYA=30, minimum FC is 2 and target FC is 4.
Daily FC demand has been 3.5-4.0ppm, and I've found that raising FC to 10ppm at night allows me to remain safely above the minimum FC=5ppm for CYA=60ppm.
The question is, what if my CYA is actually 30ppm? Is FC=10ppm too high to swim in? I vaguely remember someone saying that it's ok to swim as long as FC is under shock levels, which for CYA=30ppm is 12ppm.
BTW, the pool store test result for my CYA is always minimum 100ppm (as high as they will test).