Step one - Wash the pool with Tri-sodium Phosphate (TSP)

Every pool must firsrt be scrubbed with TSP. This product can be bought at Home Depot and is now available in liquid form. The TSP should be applied in 15 to 20 foot sections and immediately rinsed after each section. Do not permit mixture to dry on the wall.
A pump should be kept at the bottom drain to evacuate the liquids at all times.

Step two - Acid wash the pool

The acid washing causes etching of the pool. Depending upon the hardness of your water the acid content will very. First add water to a 5-gallon plastic pail then add the acid according to directions that are on acid container. Always wear gloves and goggles.
Pour acid solution onto the walls in sections by walking around the top of your pool. When the bubbling stops rinse immediately. Do not permit the solution to dry on the wall. When the walls are completed then do the floor.

Step three – Wash the pool again

Immediately after the acid wash, the pool must be scrubbed once again with the TSP, which will neutralize the acid. The TSP and acid will act as a barrier if the pool is not washed down 100%.