Drain the pool, and scrub the sides of the pool to remove algae and other debris. Remove leaves and other items from the bottom of the pool, and prepare the acid wash by pouring 1 gallon of acid wash into a watering can and adding 1 gallon of water to the acid. Pour the acid mixture onto the plaster in 10 foot sections, and rinse the area thoroughly after 30 seconds.
Always follow the manufacturer's instructions when combining acid wash with water. Do not allow the acid wash to remain on the plaster for long periods of time to prevent damaging the pool, and wear protective gear, including a respirator, goggles, boots and gloves, when working with acid wash. Neutralize the rinse water that collects in the deep end of the pool by spreading 2 pounds of soda ash per gallon of acid over the water.
Use a pool brush attached to a pole to stir the ash into the water, and drain the water using a submersible pump. Drain the water directly into a storm drain or another appropriate drainage system. Repeat the cleaning process a second time if necessary. Work with a second person so that one person can pour the acid while the other rinses the pool.