A Guide to Using Muriatic Acid for Pool Maintenance

  • By: John Parker
  • Last Updated: February 21, 2023

Muriatic acid, also known as hydrochloric acid, is a commonly used chemical in the maintenance and cleaning of swimming pools.

It is normally used to lower the pH and total alkalinity levels in pool water to ensure that it is safe for swimming and to prevent the buildup of harmful bacteria. However muriatic acid can be a dangerous and highly reactive chemical so it is important to understand how to use it properly and safely.

In this article, we will provide clear information on what muriatic acid does for a pool and the key considerations for its use, as well as its benefits and potential drawbacks.

What does muriatic acid do for a pool

Table of Contents

Why use muriatic acid in pools

The pH level of a pool is an important factor in maintaining a healthy and balanced pool environment. The ideal pH level of a pool should be between 7.2 and 7.8.

  • If the pH level is too low, the water can become corrosive and damage the pool and equipment.
  • If the pH level is too high, the water can become cloudy and cause skin and eye irritation.

Muriatic acid is used to lower the pH level of the pool water to bring it within the ideal range.

The importance of maintaining the pH level in a pool

The ideal pH range for pools

The ideal pH range for a swimming pool is between 7.2 and 7.8. This range is considered neutral and provides optimal conditions for swimmers and pool equipment.

When the pH level is within this range, the water is less likely to cause skin and eye irritation, and the chlorine in the water will be more effective at killing bacteria and other harmful substances.

Problems with low and high pH levels

If the pH level in a pool is too low, the water can become corrosive and damage the pool and equipment. This can lead to expensive repairs and decreased enjoyment of the pool. Additionally, low pH levels can cause skin and eye irritation, making it uncomfortable for swimmers.

On the other hand, if the pH level is too high, the water can become cloudy, reducing visibility and making it difficult to see the bottom of the pool. High pH levels can also cause the chlorine in the water to be less effective at killing bacteria and other harmful substances.

How muriatic acid adjusts pH level

Muriatic acid works by releasing hydrogen ions into the pool water, which in turn decreases the pH level.

The pH level is a measure of the acidity or basicity of a solution and is measured on a scale of 0 to 14.

  • A pH level of 7 is neutral
  • A pH level less than 7 is acidic
  • A pH level greater than 7 is basic.

By adding muriatic acid to the pool water, the hydrogen ions lower the pH level, bringing the water closer to the ideal range of 7.2 to 7.8.

How much muriatic acid to lower pH in pool

Klean Strip Green Safer Muriatic Acid Jug 128 Oz (Pack of 4)

How much muriatic acid to add to pool water to adjust the pH level depends on the size of the pool, the current pH level, and the desired pH level.

It is important to measure the pH level of the pool regularly using a test kit or test strips and to add the appropriate amount of muriatic acid to the pool.

Too much muriatic acid in pool water can cause the pH level to become too low, which can be dangerous for swimmers and can damage the pool and its equipment.

This table shows how much muriatic acid to lower ph in pool that holds 10,000 gallons to reduce the pH down to 7.5:

pH LevelMuriatic Acid (ounces)
85 – 8 ounces
910 – 16 ounces
1016 – 24 ounces
1124 – 32 ounces
1232 – 40 ounces
1340 – 48 ounces
1448 – 56 ounces
Muriatic Acid Pool Chart 

For larger (or smaller pools) use the same proportion so to lower the pH from 10 in a 25,000 gallon pool add between 40 and 60 ounces (multiply by 2.5).

Although I have used muriatic acid at times, I rarely need to use it. This is largely because I do not normally use liquid chlorine to shock my pool. Liquid chlorine has a pH of 13 so using it is likely to increase the pH and require muriatic acid to lower it again.

How to use muriatic acid to pool

It is important to always add muriatic acid slowly and to test the water at intervals to ensure that the desired pH level is reached and maintained. Adding too much muriatic acid can lead to a dangerous drop in pH, so it is always best to add it in small increments and to monitor the water’s pH level regularly.

You should also avoid adding the acid directly to the pool, as it can cause skin and eye irritation. Instead, add the acid to a bucket of water and stir it in. Then slowly pour it into the pool walking around the edge as you do to distribute it evenly.

Run your pool pump to ensure the acid is mixed throughout the pool.

Safety when adding muriatic acid to pool

what does muriatic acid do to a pool

Proper handling and storage of muriatic acid

Muriatic acid is a highly corrosive and strong mineral acid, and it is important to handle and store it properly to avoid injury. It is important to store it in a cool, dry place away from flammable materials and to keep it out of reach of children and pets.

Never mix acid with any other chemicals.

Protective gear to wear when adding muriatic acid to the pool

When adding muriatic acid to a pool, you should wear protective gear to avoid skin and eye irritation. This can include gloves, eye protection, and a long-sleeved shirt. It is also important to avoid inhaling the fumes from the muriatic acid, as they can be harmful.

Precautions to take to avoid skin and eye irritation

If muriatic acid comes into contact with the skin thoroughly wash the skin in clean water. If muriatic acid gets in the eyes, it is important to rinse them immediately with water for at least 15 minutes and to seek medical attention if necessary.

Using muriatic acid with a vinyl liner

If you have a vinyl-lined pool you should use muriatic acid sparingly as there is a possibility it may affect the liner, particularly if you have a patterned liner.

You would be better advised to use dry acid instead of muriatic acid to lower the pH if you need to.

Using dry acid vs muriatic acid

Dry acid is actually sodium bisulfate which, as the name suggests, contains sulfates. Over time sulfates can build up and start to attack the structure of your pool.

Muriatic acid on the other hand is chlorine-based and is actually also produced by the body in the form of stomach acid. This will not adversely affect the pool’s structure. It is also normally cheaper than dry acid.

Muriatic acid FAQs

How often should I add muriatic acid to my pool?

The frequency of adding muriatic acid to your pool will depend on several factors, such as the size of your pool, the amount of usage, and the presence of other chemicals. Generally, it’s a good idea to check the pH level of your pool once a week and add muriatic acid if necessary. You may need to add more often during hot, sunny weather when the pH level can rise quickly.

How long after adding muriatic acid can you swim?

It is safe to swim in a pool after adding muriatic acid, but you should wait at least 15 minutes to allow the chemical to mix properly and then check the pH level of the water again to make sure it’s within the ideal range of 7.2 to 7.8. If the pH level is still too high, you may need to add more muriatic acid and wait another 15 minutes before checking the pH level again.

Can too much muriatic acid be harmful to my pool?

Yes, too much muriatic acid can be harmful to your pool. If the pH level drops too low, it can cause skin and eye irritation, and can also damage pool equipment and surfaces. It’s important to follow the manufacturer’s instructions and not add too much muriatic acid at once. If you add too much, you can neutralize the excess acid by adding sodium carbonate (soda ash) to raise the pH level back to the ideal range.

Does muriatic acid go bad?

Muriatic acid has a long shelf life, upwards of 5 years if stored properly. It may be that the container it is stored in could last for less time so you should regularly check the muriatic acid you have stored. If it is in a plastic bottle it should not be stored in sunlight.

Does muriatic acid kill algae?

Muriatic acid will not directly kill algae when added to a pool. However, using it to balance the pH level will allow the chlorine in the pool to work properly and that will kill any algae.

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