Acid washing of gunite pools: if your pool and/or spa has staining or discoloration, an acid wash may be performed to remove the surface staining, scaling, or discoloration. This can be done anytime, though it is common to perform an acid wash at the time of the opening. An acid wash is not something you want to perform every year. The process takes the top layer off of the material and could prematurely wear a surface down if done too frequently. It is a nice way to freshen up a gunite pool’s appearance after a number of years, and can make the pool feel new again! Once an acid wash is not going to be a solution any longer, it’ll be time to consider a pool renovation. NOTE: If you paint a pool an acid wash is not going to be advised.