If your pool walls feel like sandpaper, it's likely because of calcium scaling. Calcium scale is a white, flaky substance that can build up on pool surfaces. High pH levels in the water cause this scale. When pH levels rise above 7.6, calcium carbonate begins to precipitate out of the water and onto surfaces. This build-up can make pool surfaces feel rough and abrasive. Also, high pH levels can cause swimsuits to fade and chlorine to become less effective.