I just removed my cover, drained the pool and had it acid washed in prep for repainting the plaster. There is now a grey discoloration below the water line that existed prior to draining. Is is ok to paint over the grey discoloration after the acid wash or should the stain be completely removed first? If so, is this another acid wash?
Gunite pools often change colors after water is removed, and the solutions aren’t always easy to predict. The discoloration could be the water drying from the surface and leaving residual behind. It could be the material itself. If the pool has never been painted, the best solution for the pool surface may be acid wash and refill. Once a pool has been painted it will need to be repainted almost yearly and isn’t the best long term solution. If you have the budget, a new surface being applied over the old would give you the best cosmetic look. Not knowing the particulars of your pool it’s hard to know if the paint would adhere any differently to the discolored areas or not. Best of luck with your project!