I believe you can try the old bucket trick. You fill, say, a five gallon bucket with enough water to fill it pretty deeply, about the same as the pool, but not enough to sink. You can tie it to a ladder or something. Measure the water and the water in your pool. If, 24 hours later, there is an inch loss in the pool AND in the bucket, your pool is not leaking (unless there's a hole in the bucket! ). If, however, the bucket level has not gone down but the pool has, start searching for a leak somewhere.