Hydrochloric Acid

Hydrochloric Acid For Pools - What Does It Do?

Hydrochloric acid is a powerful acid that can be used in swimming pools to adjust water chemistry. While this acid is mostly used to help you to balance your water, it can also have uses in certain pool cleaning applications.

In this article we will discuss when you should use hydrochloric acid in a pool, the safety risks of using hydrochloric acid, and how to use it properly.

When To Use Hydrochloric Acid For Pools?

Hydrochloric acid for pools, sometimes referred to as pool acid or muriatic acid, is most often used to lower the pH and total alkalinity content of your water.

There are also other uses for this powerful acid, such as aiding in the stain removal process, deep cleaning certain types of filter cartridge, and acid washing.

Although this process is typically performed by professionals, highly concentrated hydrochloric acid is used to remove the toughest types of stains, including calcium scale and those caused by certain metals.

Ideal pH And Total Alkalinity Levels

Ideal pH levels in your pool range from 7.2-7.6. This range is the most ideal for your pool because it is the best pH for the comfort of the skin and eyes of swimmers, and it is also the range at which your pool’s free chlorine can provide the most effective sanitation.

Total alkalinity helps to maintain stable pH levels in your pool, and ideal levels of total alkalinity range from 80-120 parts per million (ppm). Too much total alkalinity in your pool can lead to high pH, water cloudiness, scaling, and chlorine ineffectiveness or low ORP.

Important Safety Precautions For Hydrochloric Acid

When handling hydrochloric acid, it is important to understand the risks involved.

Hydrochloric acid is considered a highly corrosive substance that is capable of causing irreversible damage to the skin and eyes. Chemical burns are possible after only a brief period of exposure, so contact with the skin should be avoided at all costs.

Hydrochloric acid can also produce irritating fumes, so it should only be handled in areas with adequate ventilation. It is highly recommended that you use gloves and protective eyewear when handling hydrochloric acid. Keep this product out of reach of children and pets.

If you would prefer to avoid the risks associated with hydrochloric acid, there is a safer alternative available. Dry acid can also be used to lower the total alkalinity and pH of your pool.

How To Use Hydrochloric Acid In Your Pool

While there are other uses for hydrochloric acid in pools, this guide will focus on how to use hydrochloric acid to lower the pH and total alkalinity of your pool.

Gather Supplies

When using hydrochloric acid to adjust your pool’s chemistry, you will first need to gather a pH and total alkalinity test kit, hydrochloric acid, protective gloves and eyewear, and a durable plastic measuring cup.

A plastic mixing bucket is also recommended, so that you can dilute the hydrochloric acid before adding it to your pool.

Test Your Pool

Before adding hydrochloric acid to your pool, test your pool’s pH and total alkalinity to figure out how much acid you need to add. This can be done using a test kit.

You should not add hydrochloric acid if your pH and total alkalinity are already adequate or low, unless you are dropping these temporarily before the use of another pool treatment.

Calculate How Much Acid To Add

After you’ve measured your current levels of pH and total alkalinity, calculate the necessary dose of hydrochloric acid. We recommend using our hydrochloric acid pool calculator to make this step quick and easy.

To use the calculator, you will need to know your current pH and total alkalinity levels, the volume of your pool in litres, and the concentration percentage of your hydrochloric acid, if available. The calculator will then tell you how many mL of hydrochloric acid to add to your pool.

Add no more than 500mL of hydrochloric acid to your pool at one time. If you have any doubts about how much acid to add to your pool, always start with a lower amount and add more acid later if necessary.

Adding too much hydrochloric acid to a pool can create undesirably low levels of pH and total alkalinity that are often sustained until the acid breaks down. This can lead to hot spots of acid in your pool, which in turn results in corrosion of your pool surface and equipment.

Add Acid To The Pool

When adding hydrochloric acid to your pool, it is encouraged that you premix this product to avoid the risk of ‘hot spots’ forming.

Hot spots are areas of concentrated acid that aren’t properly mixed in with the rest of the water. If they do not circulate properly, these can cause burns for swimmers or damage to the pool’s lining or equipment.

Fill your bucket up halfway with pool water, then measure out the appropriate amount of acid in your measuring cup. Carefully add the acid to the bucket of pool water, taking care not to splash it or breath in any fumes.

Without mixing the solution in the bucket, distribute the contents of the bucket all around your pool while the pump is running.

After adding the acid to your pool, you should run your pump for a minimum of three hours before retesting your pH and total alkalinity levels. From there, you can add another dose of acid if necessary.

How Soon Can You Swim After Adding Hydrochloric Acid?

It's best to wait at least 3 hours after adding hydrochloric acid before swimming. Make sure that the pool pump is running during this period to help the acid circulate and mix in with the rest of the pool water.

Where To Buy Hydrochloric Acid

Because hydrochloric acid is classified as a dangerous good, it typically cannot be purchased online and then shipped to the home. We recommend picking this product up at your local pool supply or hardware store.

If you need help locating a retailer in your area, you can check out our guide on where to buy muriatic acid in Australia.


Hydrochloric acid, sometimes called muriatic acid, is typically used to lower the pH and total alkalinity of your pool’s water. Although it can be dangerous to handle, its potent concentration means that a small amount of acid is capable of making big changes in your pool’s chemistry.

Do you have any questions about using hydrochloric acid in your pool? Leave us a comment down below, we’d love to help!

Louis from Pool Advisor


A chemical engineer by trade, Louis is committed to debunking myths in the pool industry by explaining the underlying chemistry and making it accessible to all.