Whether your pool looks like a swamp, or you just want a fresh, clean-looking appearance, acid-washing your swimming pool can help. Also called "drain and clean," pools need this type of cleaning when winterizing the pool isn't done correctly, or algae has taken over due to the pool not being used or maintained in a while. The acid-wash process essentially strips the top layer of plaster to reveal fresh plaster beneath, so it's not recommended to do it often. But once in a while is a great idea.
Your pool generally only needs an acid-washing every five to seven years if you regularly treat and maintain the water in it. 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.
It is best to leave the acid-wash procedure to your pool professional.