Consumption, if that's the right term, is slowing - only lost 0.5ppm in the last hour. There's less sun at this time, which I expect makes a difference. I've been wondering about volume all day - the 40-45kgal I quoted in my first post was the contractor's best guess, and seems high to me.

I've been crunching numbers since, and I don't think there's more than 35kgal in there. The pool is L-shaped; 44' long by 16.5' wide with an additional 6' at the bottom part of the "L". It's 3' deep along the shallow first 19', dropping to 8' deep at the deep end. The corners are all cut.

I also reckon 1gal 12.5% is adding about 3.4ppm based on measurements. If 1gal of the 12.5% should add 2.8ppm to 45kgal, then 3.4ppm/gal means 35k is in the ballpark. Seem reasonable?

Here's how it looked at 12:00, in case the visual helps make sense of my ramblings...

Sunday 1200.jpg