Water looks good - sparkly and clear. We're in Fresno (100+ deg. F. summer days). I've been lucky and have never had cloudy water or an algae bloom since the pool was installed (2010). But after the first year, I've had persistent staining of algae on the pool wall surfaces that are in the shade, even when FC > 2.5 ppm (which at CYA = 35 ppm, I presume should not allow algae growth). The algae brushes off easily enough, but within 2-3 days, it comes back.
I was concerned that the issue was too high a CYA (from reading this forum), so this spring I drained the pool and switched from tabs to bleach. I add bleach in the AM to reach FC = 3.6-4.0 ppm, and I lose about 1 to 1.2 ppm during the day. I see no loss of FC overnight. I maintain pH between 7.2-7.6. I can keep algae at bay if I raise FC to ca. 5 ppm, falling to 4 ppm during the day, but would rather not keep FC so high.
I make my own tests using the Taylor complete/FAS-DPD kit.
Does anyone else have this problem? Thanks for your help.
Today at 10:00 AM:
FC = 3.0 ppm
CC = 0 ppm
pH = 7.5
TA = 95 ppm
CH = 220 ppm
CYA = 35 ppm
Borates = not used