Calcium Buildup on Pool Tile
You might notice some white chalky calcium over the surface of your pool tiles. The calcium caused by hard water isn’t dangerous, but it can detract from the attractiveness of the pool. If left in place, calcium deposits can also build up, causing filter failure. Removing calcium from the tile without causing damage is possible with the use of a muriatic acid solution. The acid will strip away the calcium, leaving your tiles in pristine condition
Calcium deposits on the surface of swimming pool tiles can result in an entire pool pockmarked with unsightly white stains. Calcium stains should be cleaned when you notice them, because over time, the calcium can penetrate the tile, making the stains much more difficult to remove.
This video above does a great job explaining how to remove the calcium buildup on pool tile, step by step.