Acid Washing

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Acid washing swimming pools.

Why do pool shops tell me to acid wash my pool?

They don’t know what the stain is

You will need to buy lots of chemicals from them when the pool is refilled

Shops make about $500 profit on an acid wash

It does work most of the time but does not prevent the stains from coming back

Most regular pool shop staff lack the experience and chemical knowledge to remove serious staining.  Because of this, many pool shops will advise their customers to acid wash their pool, or even 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.

1

How to acid wash a pool.

Acid washing is a cleaning process that involves completely draining your pool and then pouring or spraying a very strong mixture (usually 50/50) of hydrochloric acid and water on the walls and floor of your pool.  This process is 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 two to three times as this process etches (eats away) the interior and reduces its overall thickness.  Those who have already acid washed their pool have told us that since the wash the interior 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 coloured interior is a thin concrete veneer that is only 4-8mm thick.  Frequent acid washing could permanently damage this thin interior.

2

What are the risks of acid washing?

If an acid wash is not done properly, it is possible that streaks from the flow of acid can permanently etch the pool surface.  Once these streaks discolour the pool surface there is no way of removing them.  It is very important to know 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.  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. Refill as soon as you can because many pool surfaces are damaged by being drained and exposed to sunlight and temperature differences.

How much does it cost to acid wash a pool?

Apart from treatment costs, an acid wash can be inconvenient and expensive.  An acid wash alone costs between $850-$4000 depending on the size of your pool and the severity of the stain.  This estimate does not include the tap water needed to refill the pool which is usually around $185 for 50,000 Litres of water from most major city councils.  Also there is the cost of the salt, pool acid, sunscreen and buffer to rebalance your pool water after it has been refilled.

Be careful with cheap acid wash prices as some 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. We have had clients 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.

What do I do if nothing else works?

Although our treatments are effective in over 95% of pools, there are some stains and marks that are not able to be treated chemically such as silica build-up, or interior aging and degradation. In these cases, we have no other choice but to acid wash the pool.  Generally speaking, if acid washing the pool does not correct the problem, then your pool will need the cement interior to be replaced.

The importance of contractor insurance.

If you decide that you want to acid wash your pool then we strongly suggest choosing a reputable contractor who has current liability insurance.  This is because very occasionally a pool can lift out of the ground as the water is drained for an acid wash.  This is called hydrostatic uplift pressure.

Most pools have a valve that normally releases the water pressure under the pool.  It is called a hydrostatic valve and it lets groundwater into the pool when needed to release the pressure.  In some older pools these valves can seize up which causes the water pressure under the pool to be very high.  In these situations pool uplift is a strong possibility after 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.

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 info@thepoolstainremovers.com.au or call us on 0416 927 837.

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