The walls and bottom of plaster pools can become rough over time because of use, chlorine and other additives in the water. While the roughness does not impact the pool's structure, it can make it uncomfortable for swimmers. In addition, the coarse texture can attract stains which can be difficult, if not impossible, to remove with regular cleaning. Once your pool's walls and floor become uneven and bumpy, you might want to consider sanding down the pool to make it more user friendly and better looking.
Drain the pool. The pool should be empty of water before you begin the sanding process.
Sand the rough areas with 80 grit wet/dry sandpaper and a sanding block. Sanding by hand will give you the most accurate results. Make sure you sand all of the areas you want to smooth out and use a step ladder if you have trouble reaching.
Sand the areas a second time with 120 grit wet/dry sandpaper and a sanding block. The second sanding will smooth the surface and prepare it for a final sanding.
Sand the rough areas a third time with 240 girt wet/dry sandpaper and a sanding block. This third pass at sanding should have the pool almost completely smooth and stains should be gone. If not, go back over the coarse or stained patch again with the 80 grit and 120 grit wet/dry sandpaper.
Run the angle grinder over the areas with 600 grit wet/dry sandpaper. This will give the pool a finished, smooth look and take care of any small gouges.
Rinse off the pool walls and floor with a hose and clean water. Drain the water and then fill the pool.