If your pool has developed algae due to sitting unused for a long period or not adding the proper chemicals for maintenance, acid wash is an effective method of cleaning and restoring the look of the pool. Gunite is a common surface material, comprised of cement and sand, and is applied through a pressure hose around the walls and floor of the pool. Whether you want to clean the gunite surface or prepare the pool for re-patching, an acid wash is ideal to remove the buildup of algae, mineral deposits and pool chemical stains.
Submerge a pump into the pool to drain the water into a safe area. Pool Center suggests you contact the local water company for water removal regulations so you safely remove the dirty water without harming plants or animals.
Scrub down the walls and floor of the pool to remove any dirt or debris as it is draining with a stiff-bristled scrub brush. Walk around the pool with caution, as the floor may be slippery. Wear protective gear such as non-stick shoes or boots, rubber gloves, goggles and breathing mask to protect against acid fumes or splash back.
Mix equal parts of muriatic acid and water (1-gallon increments) into a large bucket. Pour the acid into the water and spray down the walls of the pool with the hose. Leave the hose running, as you will use it frequently during the acid wash. Apply a small amount of the acid wash to the wall to test. The wash should fume and bubble on the surface. If it does not, add more acid to the water cup by cup, and test each time until it bubbles on contact.
Pour the acid mixture from the top of the pool wall in 5 to 10 foot sections. Allow the acid to run down the walls and into the deep end of the pool. With an acid-safe brush, scrub the gunite surface in a circular motion for no more than 30 seconds. Scrub around the entire pool until the gunite is clean. Hose down the entire pool to remove any acid from the surface.
Neutralize the acid wash that has accumulated at the bottom of the pool. For every gallon of muriatic acid you used, pour 2 pounds of soda ash into the water. Combine the soda ash with the acid wash using a long pole or broomstick.
Pump soda water out of the pool into a safe area, away from pets, plants and storm drains. Rinse the pool two or three times to remove any trace of acid or soda before re-plastering or filling with water.