Is there a way to find a hole in a liner of a 27' round above ground pool? The water keeps draining out below the filter basket and on one side I can tell air is under the top of the liner. I've filled it twice, but it drains within a day. I don't see any water outside of the pool anywhere, Help?

Once it drains down to the basket does it stop? To drain this much there must be a sizable leak. Where is the ground spongy?

I agree. If it stops below the skimmer, then odds are that you have a leak in the inlet line to the pump. If it drop to the return in the pool then you have a problem in that line. If it continues to drop then what I do is leave the pump off for quite some time to allow the water to calm down. Slip in with your mask and snorkel and start around the seam etc with a plastic syringe with mike or cream preferably. REd Food dye in water works as well. When you find the leak you will see the cream or dye get sucked in. You will need a under water vinyl patch kit to repair this type of leak. Most time I find leak where the wall meets the floor. Toe rings seem to catch liners that have a poor sand cove.

If your back wash hose/line stays unrolled away from pool, check to see if water is coming out there. Your filter multi port valve may be allowing water to go out backwash line.