O yay! It held!

The pump timer shuts the system off at 0400. This morning around 0900 I checked the pot. It was full of water with only the merest little air bubble the size of a nickel touching the domed lid. No drain-down!

I cannot even begin to explain that. All I did was backwash/rinse and remove the weir. Yes, I did epoxy what might have been a crack in the pot but remember, I filled it after that and the pot drained again.

It's holding now—for now—and so I'm just going to pat myself on the back and tell myself 'you rock!'

Al, you're right, it's an above-ground with the equipment below the water level.

CarlD, I do have a ball valve on the suction pipe from the skimmer to the pot. I have to turn it and the valve to the return off whenever I open the pot or else, a flood!

Greg, it makes sense that there is an air leak somewhere. If I'm reasoning this out correctly, the pump shuts off and, in the absence of an air leak, there's a vacuum in the pot. If there's an air leak the air would push the water back (into the filter?) until a pressure equilibrium is reached, which results in a half-empty pot. When the pump is turned on the pot is half full of air and mo additional water can get in to fill it.

Or am I making this up? Sounds good, tho9ugh, doesn't it?

I will check all fittings to make sure they're tight, don't know what else to do. IF this problem comes back.

Thank you all very much for caring about this and for your input.