How To Acid Wash A Swimming Pool (step-by-step)

by T. Duff on April 27, 2009

Here’s What You Need To Know If You’re Planning On Doing An Acid Wash To your Swimming Pool.

Sidenote: An acid wash should not be administered to a vinyl or above ground pool. :)

Who can do this? Anyone who’s willing to get a little dirty.  This can be done by pool owners who are looking to save a few bucks – there is labor involved.  Make sure you wear jeans, protective boots, goggles, rubber gloves and a respirator – the acid fumes can be very strong. This is not something to take lightly.

An acid wash is also called a drain and clean or an acid bath.  An acid wash becomes necessary if the pool has become a black lagoon (can often happen if winterizing has not been completed properly).  This is also a great way to eliminate/reduce staining.

What an acid wash really does: The purpose of an acid wash is to remove a very fine layer of the pool surface – bringing out a “new” coat.  When done properly, an acid wash can really make the pool surface look near new again.

A general rule of thumb for determining the need for an acid wash is if you can see the bottom of the pool, most of the time, you can bring it back to life with chemicals, some elbow grease and adequate filtration/circulation. If the floor is not visible, the cost of the chemicals and labor will generally be greater than the acid wash charge, and take quite a bit longer. Also, extensive and repetitive algae problems will stain plastered pools, making an acid wash the recommended route to take.

An acid wash is, put simply, purposeful stripping of a tiny layer of plaster, exposing fresh plaster beneath. One should not do this every year. If you have consistent staining – there’s something taking place in the chemistry (test for metals, TDS and calcium counts in the water). Most plaster coats (whitecoat or marcite) are in excess of 1/2″, so a few careful acid washes should not hurt.

If the staining is very light you may want to consider doing a pressure wash or a very light acid wash (consider 3 parts acid/1 part water – do a small area and see how it looks).

You may also decide on an acid wash not because of swamp conditions, but just to bring out a brighter, whiter finish. Mineral stains and/or deposits, chlorine stains, even dirt stains…an acid wash is always a dramatic aesthetic improvement.

If your pool has had years of algae blooms, and if your pool seems to grow algae overnight or just bloom very easily….changing the water and acid washing the surfaces algae sticks to can give you an algae free summer.

Be extremely careful in working with muriatic acid. Pool technicians and professionals are specially trained in its application and wear protective clothing and breathing apparatus during the acid wash. To protect our environment, the acid/water waste should be neutralized with soda ash prior to its being pumped to a safe location.  You can (and should) have the soda ash at the bottom of the pool to immediately neutralize the acid as it flows down during the wash.

Phase 1 to an acid wash: As you drain the pool, wash it down (scrub if necessary) to remove all algae, leaves and any other debris.

Phase 2: When the pool is clean and empty, you can begin to acid wash the plaster. Put on protective clothing and rubber boots, goggles and wear a breathing mask designed for acid fumes.

Phase 3: Proper mixing of the acid.  Add 1 gallon acid to 1 gallon water in a flower watering can.  Always add the acid to the water – NOT water to acid.  Wet down the wall with a hose. Keep the hose(s) running at all times, without a nozzle on it. Pour the acid/water mixture down the wall, from top to bottom, one 5-10 foot section at a time.

Do not allow the acid to sit on the plaster for very long. Usually 30 seconds is plenty sufficient. Use an acid brush to scrub the surfaces and move the acid around. Rinse quickly and thoroughly.

Phase 4: Once the acid wash has been completed, make sure the pool surface is rinsed completely – don’t take any chances here.  Acid that sits on plaster/pebble too long can “burn” or etch the surface.

Also try to prevent the acid from wearing a channel path from shallow end to deep end. This can create a worn stripe on the floor.  If this does happen, make sure it’s quickly neutralized.

If the 50/50 solution isn’t strong enough, you can increase the acid strength or the hang time (before rinsing), or scrub harder. To maximize the effectiveness of the process you can also repeat the acid wash twice using the same strength mixture.

The surface, however, should be completely hosed down before the second wash.  You don’t want to damage or “burn” the plaster.

After the acid wash, the bottom of the pool will be filled with a foamy, acid puddle. This needs to be neutralized before pumping out. A good rule of thumb is to use 2 lbs of soda ash per 1 gallon of acid used.

Broadcast the ash over the puddle while stirring with a pool brush on a pole. Use a small submersible pump with a hose to pump out the remaining acid water. Be careful where you pump it to. Even if properly neutralized, it may destroy plants, grass, animals, etc.

** You’ll end up with a puddle at the deep end of the pool – make sure this acid is neutralized and use lots of water as you’re pumping it out.  It can leave an “acid ring” on the perimeter of where the water sits.

Don’t rush the job and be safe. The fumes can be very strong, and very dangerous.

Phase 5: Let’s clean up.  Spray off before exiting the pool. If you do get acid in your eyes, rinse for 10-15 minutes – if the burning persists, consult your physician or visit the hospital.  Make sure there’s another person around when you’re completing this project.

Acid on the skin won’t usually burn too much (unless it’s over a cut or scrape), just rinse quickly, until the burning goes away.

If your pool is vinyl lined, acid is not used. Detergents, conditioners and good ‘ol elbow grease will remove the “slime”. The liner must then be “reset” with a vacuum to ensure proper fit during filling. Also, be sure not to completely drain the vinyl pool.  There can be problems getting the liner to reset properly, and there is also the possibility of the caving in (you don’t want that).

Although pool companies will vary in price for this service, some rough numbers are as follows:

  1. Drain = $125.00
  2. Acid Wash = $125-200 (depending on condition of surface)
  3. Start up chemicals = $75-150 (depending on size of pool)

Total = $325 and up.

You can do this yourself for under $125 – using the chemicals referenced above and start up chemicals (salt (if you have a salt pool), liquid chlorine, shock, conditioner).

Many may choose to hire a company to do this after seeing the process – the most important thing is to be safe and make sure it’s done properly.  If you choose to hire someone or a company, be sure to watch them so next time you can do it yourself.


And that’s how you acid wash a swimming pool.

All the best,


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