Limescale forms on pool walls when they are filled with hard water. Hard water contains minerals like lime and calcium that create a white, crusty substance as the water evaporates. There are several limescale removing solutions on the market, such as LimeAway, Blue Wave, Jack's Magic Blue Stuff and Stain Away. All of these chemical solutions work to break limescale away from the walls and floor of the pool.
Drain your pool so you can get into it and access the floors and walls.
Apply the limescale removing solution to areas of lime build-up. If you do not have limescale removing solution, pour white distilled vinegar or apple cider vinegar into a spray bottle and spray the sides of the pool with it. Allow the solution or vinegar to sit on the limescale for five minutes.
Use a tile cleaning brush or a non-metallic scrub brush with stiff bristles to scour away the limescale. If it persists, spray more vinegar or solution onto it and scrub again until it dissolves and comes off the walls.
Use a garden hose with a spray nozzle to rinse the pool walls thoroughly. Allow the limescale and cleaning solution to drain from the pool.
Refill your pool once the limescale and cleaning solution are out of the pool.