OTO and CYA and TC, oh my! What's being measured?

[aquarium]

Thanks Janet,

Yeah, and we have -very- high calcium hardness here, so I don't want to add more.

Just took a couple of tests at high noon here. I can see the dip in the chlorine when taken across the pool from the returns, so the low CYA is having the expected effect. Near the returns it's almost up where I want it. I'm letting the pump/chlorinator run a couple of hours after the sun is off to punch it back up for the night.

The way it's set now a single 8 ounce puck will last most of a week. (15,000 gallon IG concrete) Before this water change I was going through nearly one a day.

Tom

PS: It's not a 'pressurized' chlorine system, just a vertical PVC pipe with water in/out and a ball valve, with the pucks inside. I think it's also called an erosion type feeder.