I tested CH for the first time yesterday, after having water in the new pool for a month. The level was [EDIT] 130, which is fairly short of the 250-650 range. I called our pool maintainer and asked if he could bring by some calcium chloride on his next visit to bring it into range. He said that he would be happy to do so, but in his experience it would be better not to because the CH level will naturally tend to increase over time, and will tend to speed up the "unavoidable" (in his words) accumulation of white deposits on the tile. Thank you, as always, for your expertise. Perhaps in another 10 years I'll become a somewhat useful contributor around here too.