Thanks Richard, for the K2006 info.

I only check CH once or twice a summer, having a vinyl pool. But I do always check CYA with my weekly test and keep extra reagent on hand always. TA's easy to test every week, too. Though--full disclosure--I don't run the full suite every week at all now that I have an SWCG. But when I'm setting up in the spring I do, and more often if there's a problem.

But as Richard says, the FC/CC/TC and pH can change in hours which is why the daily tests are recommended...2-5 minutes a day and you'll have a clear pool all summer.