Swimming pools blog

Greetings (and happy Summer solstice to our Druid friends),
Today was the longest day of the year, with 14 hours and 44 minutes
of daylight locally, most of it sunny. Our pool is sans cover (has
been for a week) and yet the water temp is 89.7 degF (32degC) at
this hour.
Not much else to report, the water is clear and needed to be topped
off about three inches (75mm) for the month to date. I noticed the
pH has been steadily decreasing this season, and it hit 6.2 last
week. That’s the lowest end of the test scale, so I checked TA at
the same time (a healthy 120ppm), and decided to bring the pH up
gradually with soda ash.
I’ve dumped about 7.5 pounds (3.4kg) in over the past week and the
pH has risen to 7.5, not bad, but I’d rather not add any pH
adjustment chemicals. It’s a Gunite plaster pool, which has
previously registered above 7.8 pH. (This is a new test kit, and

readings were confirmed with a second test kit).
To prevent a return of black algae I’m adding polymer Algaecide (the
blue ink kind), 50% strength, weekly; perhaps that is affecting the
pH?
Comments Welcome!
And Happy Alban Heruin,
Peter