Is there a chance that the water that is leaking, is undermining the pool by washing away the dirt under it?
How many gallons of water do you think you are using/wasting? You say your pool is 18 x 33, 594 square feet, and you replace 1/4 " per day. (I'd do the math but it's not my problem)
How much are you paying for the water you are using? Do you have a water bill or are you just paying the electric bill to run a well pump? If a well pump, how much life are you taking away from it by filling the pool?
Can you block the pipe at the drain by placing something over it for a few days to see if it is leaking there?