does the water level in the pool drop when the pump isn't running ?To check this out, leave the pump off for 24 -48 hours then check the level again.This will tell you how deep you will have to dig to find the leak. If the leak is in the line to the pump, you should find bubbles in the return outlets as well. If the leak is in the return line from the pump to the pool, you probably will have a swampy area (or at least a wet area ) in your yard in the vicinity of the leak