Acid washing a swimming pool – without draining

Remember, acid washing is not ‘stain removal’, it’s ‘surface removal’.  It works by using strong acids that etch and dissolve the smooth outer layer of your pool surface!  The stains are removed because the cement surface of the pool is dissolved during the acid wash.  After a pool acid wash, many owners say that this process has left their pool surface feeling rough, blotchy and streaky.

Most regular pool store staff lack the experience and chemical knowledge in pool stain removal. Because of this, many pool stores will suggest to acid wash pool surfaces when it is not required. In some cases, they even suggest that clients install a new interior to remove the staining! This is often because they simply don’t know what else to suggest. In most cases, we can chemically remove the stains without draining the pool.  We are the experts in pool stain removal.

Acid Washing 2
Acid Washing 3

Why do pool stores recommend acid washing?

  • They don’t know what the stain is
  • You’ll need of chemicals when the pool is refilled
  • Pool guys make about $500 profit to acid wash pool surfaces
  • It does not prevent stains from returning

What does Acid Washing do to my pool?

  • Reduces life of pool surface
  • Makes pool surface more coarse
  • Dissolves cement that bond pebbles
  • Can sometimes cause surface cracking

How to acid wash pool surfaces

Acid washing is a very aggressive cleaning process that involves completely draining your pool and then pouring or spraying a very strong mixture (often 50/50) of muriatic acid and water on the walls and floor of your pool. This process is sometimes repeated several times to remove stains. After this process is complete your pool is then filled with water once again.

Most pool interiors such as pebble, glass bead, plaster or Crystal Quartz are not designed to be acid washed more than one to two times over the life of the pool.  This is because this process etches (eats away) the interior and reduces its overall thickness. Often, those who have already acid washed their pool have told us that since their acid wash that the interior now feels rough. This happens because the cement that is normally between the individual pebbles or beads is eaten away by the acid leaving the pebbles more exposed.  Remember your pool’s cement interior is a very thin veneer that is often only 1/8 -1/4 of an inch thick. Therefore, if acid washing is not done correctly it can permanently damage the pool.

Risks of acid washing your pool

If an acid wash is not done properly, it is possible that streaks from the flow of toxic acid can permanently etch parts of the pool surface. Once these streaks appear, there is no way of removing them because the cement is permanently dissolved. Therefore, it is very important to know exactly what you are doing and be very careful when acid washing a pool.

Acid washing can be an effective way of removing pool stains but it should only be done if absolutely necessary. Also, we understand that there are situations where there is no other choice. However, if your pool is left empty for an extended period, the pool surface most likely will de-laminate (or separate) from the structure of the pool – particularly if your pool interior is over 10 years old. So please refill as soon as you can because many pools are damaged by exposure to sunlight and temperature differences.

Cost to acid wash a pool

Aside from treatment costs, an acid wash can be inconvenient and expensive. For example, to acid wash a pool alone costs between $650-$3,000 depending on the size of your pool.  Also the prices does change depending on the severity of the stains. Importantly, this price does not include the city water needed to refill the pool.  This is often around $95 for 10,000 Gallons of water from most cities. Finally, there is the additional cost of the salt, pool acid, sunscreen and buffer to re-balance your pool water after it is refilled.

Remember, be careful with organizations who advertise cheap acid wash prices.  In some cases, these unethical contractors will approach you for more money half way through the wash if the stains are not releasing easily. They will argue that extra time and materials are needed to remove the stains. A few years ago, we had one client pay over $2,500 for an acid wash when the actual price they agreed on was less than $900. This scenario can be a very stressful and uncomfortable situation for pool owners.

The importance of contractor insurance

If you must acid wash your pool, we strongly suggest choosing a reputable contractor who has current liability insurance. This is because very occasionally, when the water is removed, the sides of the pool can buckle, crack  or lift out of the ground. Importantly, the damage from uplift damage is not repairable.  So, to help prevent this, most pools have a hydrostatic valve.  This valve normally releases any water pressure under the pool.  However, in older pools, these valves can seize up completely and block water flow. This means that the water pressure under the pool becomes very high. So in these situations, pool uplift is a strong possibility when the water is drained.

When this uplift occurs the pool is irreparable and an entirely new pool is required as you simply cannot push the pool back down. You will require your contractors insurance to build an entirely new pool should this happen to you.

Pool lifting out of ground
After being drained for an acid wash the hydrostatic pressure pushed this concrete pool out of the ground during refilling

Need advice on acid washing?

You can speak to a stain specialist about your pool today. There is no cost or obligation and we are happy to look at pictures and talk with you before we send a kit or visit. Email pictures to or call us on 213 275 0333.

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