Son-In-Law and Daughter just bought a house with a pool. Ingound plaster, guess about 18,000 gallons in the Dallas area. There are many spots where the plaster is worn through to the concrete underneath. Some places like stair edges, maybe, but a line by the light, some large patches (baseball to softball sized) in the curve, couple more smaller ones on the vertical walls, apparently here and there. Not chipped, but looks like it is worn as the sides are smooth beveled (almost like it was sanded down to the concrete). Anyone ever seen this before?
Prior owner used a Polaris 360 as the cleaner.