When to Acid-Wash a Swimming Pool

If your water is clear and clean, your pool doesn't need an acid-wash.


The process of acid-washing your pool removes unsightly stains due to hard water and algae buildup. Once your water begins to look murky and unusually green or black, it's likely that your pool could use an acid-wash to clean it up. While you can perform this process yourself, it's best to leave it to a professional service to avoid damaging the plaster surface of your pool.

The Pool from the Black Lagoon

Without regular maintenance, your pool water will begin to allow the growth of algae. Algae growth that sits in your pool for months or more at a time will stain the porous plaster of the pool so deeply that you won't be able to remove it with regular scrubbing. Generally, if you can't see the bottom of your pool through the slimy water, it's been sitting long enough to warrant an acid-wash. Another sign that your pool needs an acid-wash is the quick growth of algae after scrubbing it. Algae spores can burrow deep inside the porous plaster and continue to bloom, which the acid-wash should completely eliminate.

Scrub a Dub Dub with Acid in the Tub

To acid-wash your pool, you'll need to drain all of the water out of it, using a pump. Wet the drained pool's walls with a hose. Mix equal parts hydrochloric acid -- also referred to as muriatic acid -- and water to spray the sides of the pool. Scrub the acid mixture into the plaster surface for about 30 seconds, using a brush. Wash away the acid with water to prevent it from permanently etching the plaster. Depending on the depth of the stains present in the pool, you may need to repeat this process. Once complete, neutralize the acidic water with soda ash and then pump the rinse water out of the pool.

To Acid-Wash or Not To Acid-Wash

Your pool generally only needs an acid-washing every five to seven years if you regularly treat and maintain the water in it, recommends the Bratton Pools website. Acid-washing your pool more often can damage the plaster coating inside the pool because the acid strips away a small layer of it each time you do it. Rather than acid-washing a slightly dirty pool, manually scrub it without any acid or with a chlorine solution to avoid damaging the plaster. This may be enough to clean the pool. Note that you should never acid-wash vinyl-lined pools, which only require cleaning with detergents and conditioners.

Acid Is a Dangerous Thing

While you can acid-wash the pool yourself with chemicals found in any pool supply store, if you don't know what you're doing, you could seriously damage your pool or injure yourself. When acid-washing a pool, you need to wear protective equipment due to the caustic nature of the chemicals, which can burn your skin and cause respiratory damage if inhaled. For safety reasons, always perform an acid-wash with at least one other person helping you. Improperly washing your pool with acid may not only damage the plaster, but could lead to discoloration. Consult a professional pool cleaner regarding acid-washing to avoid issues with your pool.

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