For the past two months, testing the TA every two weeks, I've noted a very slow but steady rise in the TA. Past three weeks of daily pH testing has shown steady at about 7.5
When I filled/opened the pool, TA was 190, same as fill water. Lowered it using acid/aeration to ~100.
Test this morning showed 160.
I've had to add water several times, but no more than 2" at any one time.
Fill water at filling showed 190, today's test shows 280. Problem at the water plant?
I'm guessing that I've answered my own question as to why the TA is rising, but that doesn't answer why the pH would be rock steady through this.