Pool walls usually come in 48, 52 or 54 inches high. When above-ground pools first started being manufactured almost all pools used 48” walls. You typically fill a pool 4 inches from the top and have sand on the bottom so those pools actually held 3’6” of water. Many people wished they were deeper so the manufacturers started making 52 inch tall pools so that they would hold nearly 4 feet of water at 3’ 10”. Now the most popular pools are 54” tall and they can actually hold 4’ of water. Two inches may not seem like a big difference but you will certainly notice it while you are swimming.