I have to dump out my 20k gal pool and before refilling I plan on washing the walls is there a recommended PSI for plaster walls? I might repaint as well just wondering about which pressure washer I should rent.
Yes I understand the many risks however the water is almost a dark green and the walls have a deep green I cannot get out by brushing. There are no visible deep cracks, however there are about 4 small spider web cracks but they are barely visible. I assumed my best course of action was to drain water and wash and refill.
You have algae. It may or may not be a good idea to exchange the water based on water chemistry results. The algae can be eradicated by following the SLAM Process. But first you need your own proper test kit (see Test Kits Compared) to see what the parameters of the water chemistry are.
Pressure washing will not get rid of the algae. Algae is a chemistry problem, not a filtering or cleaning problem.