I tried to post this yesterday but apparently the forum crashed right when I hit submit.
We went on vacation last week and the day after we left the person watching our pool reported that the water had gone below the skimmer openings. She added water but came back several hours later to find it had dropped again. I just had her shut the pump off until we got home and I could regroup. I'd had a leaking skimmer that I patched and assumed that my patch had failed, but it seems now that there is only a leak when the pump is running. If the pump is off the pool doesn't drop at all (I'm sure there's evaporation, but not a noticeable drop over 1-2 days)
I found a weeping leak where the pipe exits the pump, but it's pretty minor. I lost 1-2 inches with the pump running for 10 hrs. Pool surface area is around 700sqft, so at a minimum that's about 43 gallons/hr which I think would be a pretty noticeable leak.
There's very little exposed plumbing and everything is dry other than the little weeper around the pump exit. Is there anything else easy I can go looking for before tearing out concrete?