It is an old IG pool....23,000 concrete/plaster. We are losing water both with the pump on and off but we lose more with the pump running. Last night (over about 8 1/2 hrs) we lost about an inch and half. The skimmer was intermittently sucking air this morning

Would plugging the return jet and skimmer and turning the pump off and measuring water loss tell anything? I haven't done that yet. I am beginning to think that the filter is not the problem. I am getting very discouraged. And on top of that I'm having trouble getting the water to stay clear.

I guess I should just call a pool place to come out.

Again, thanks for everyone's help.