Calcium Scale
Calcium scale forms on pool surfaces due to very hard and out-of-balance pool water. Calcium scale is usually uniform and covers both plaster and pebbles in a pool. Calcium scale usually feels rough, like sandpaper, on the pool surfaces.
Calcium scale can occur on plaster, vinyl liner, or fiberglass pool surfaces.
Calcium scale is different then waterline scale on tiles, evaporative scale on surfaces outside of the water, efflorescence, or calcium nodules.