Acid washing a swimming pool – without draining
Remember, acid washing is not ‘stain 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 an acid wash, many pool 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 to remove serious staining. Because of this, many pool shops will suggest to acid wash a swimming pool 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 because we are the experts in pool stain removal.
Why do pool shops recommend acid washing?
- They don’t know what the stain is
- You’ll need of chemicals when the pool is refilled
- Shops make about $500 profit on an acid wash
- It often works but doesn’t 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 a pool
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 hydrochloric 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 or Quartzon 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 3-7mm 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 delaminate (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, an acid wash alone costs between $850-$4,000 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 tap water needed to refill the pool. This is normally around $185 for 50,000 Litres of water from most city councils. 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 people 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. For example, we had one client pay over $3,500 for an acid wash when the actual price they agreed on was less than $900. This scenario can be a very stressful situation for pool owners.
The importance of contractor insurance
If you must acid wash your pool then 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. 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.
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