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How is Muriatic Acid Used in Swimming Pools?

What is Muriatic Acid? 

Muriatic acid is a chemical that can be used to manage or balance the alkaline levels in a swimming pool. Excessive alkalinity in a pool can have a detrimental effect on the overall health of your swimming pool. High alkalinity can cause a whole myriad of problems such as the development of harmful limescale in the pools circulatory system, it can also cause an overall imbalance in the pH levels of your swimming pool. Adding muriatic acid to your swimming pool water is a relatively inexpensive way of managing alkalinity levels in your pool. 

What is Muriatic Acid? 

Muriatic acid is another name for hydrochloric acid, other names for muriatic acid are acidum salis or spirits of salt. It is often used for descaling kettles or other metals, balancing alkalinity levels in swimming pools, for purifying salt and for cleaning. 

Muriatic acid is actually found in the human gut. It facilitates the process of creating an alkaline environment in the gut, it also works as a digestive aid as well as destroying pathogens and tiny organisms that could cause gut infections. 

Muriatic acid pools can contain a certain amount of muriatic acid to control the pH levels in the pool. Highly acidic pool water could be detrimental and highly alkaline water can also cause problems, therefore, it is vital that pool water has the right balance of acid and alkaline, perfect pH level to avoid damage to pumps or filters. 

Muriatic acid has a relatively low concentration of hydrogen chloride in comparison to the muriatic acid products you will find available in most homeware shops. There is a specific type of muriatic acid that is used for swimming pools. It is best to only use specially formulated muriatic acid to balance the pH levels in your pool, as opposed to the standard muriatic acid that you can find in stores. 

Often the muriatic acid that is used to clean and maintain cartridge filters is the same solution that can be used to manage the pH levels in your pool. 

Reducing high Alkalinity can be a challenging task if you don’t know what you are doing. To get an idea of how the pH level that you need, consider 100 to 125 parts per million. High alkalinity can be damaging but over time, high alkalinity levels usually balance themselves out without the need for extra chemicals such as muriatic acid. 

High alkaline levels can cause problems such as algae formation therefore, if you can, address the problem before it escalates. 

When the pH level of your pool is too high, it can eventually lead to excess calcium which can result in limescale issues. Limescale problems can eventually block your circulatory system and filters. Reducing pH levels will automatically reduce alkalinity levels too therefore, using muriatic acid to balance out the alkalinity levels instead of waiting might just be the best thing for the overall health of your pool water. 

You should try to get the pH levels to around 7.5 or 7.6 on the pH scale. To avoid significant changes in a short period, add the chemicals gradually and keep testing, you need to slowly fix the alkalinity problem instead of rushing the process. 

Low pH and High Alkalinity 

Typically, low pH should equal low alkalinity, they generally go hand in hand. However, it is possible for pool water to have low pH and high alkalinity. This is often the case when there is an excess amount of cyanuric acid in the pool water.  You can fix this problem by adding muriatic acid gradually. 

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How to Reduce Pool Water Alkalinity Using Muriatic Acid 

Often a product called pH decreaser is used to lower alkalinity in pool water, it is mostly made up of a chemical called sodium bisulphate. However, you can use muriatic acid instead, it is cheaper and often readily available in hardware stores or online, it is vital that you purchase the right type of muriatic acid, however. The type that is typically used to clean cartridge filters is suitable for lowering the alkalinity levels in pool water. 


Be aware of the dangers of using chemicals like muriatic acid. It is extremely caustic and it will burn your skin if you touch it. Therefore, before you start using muriatic acid, you need to ensure that you have certain safety items. You are going to need: 

  • Safety goggles or spectacles 
  • Special gloves (suitable for acid use) 
  • Special apron (suitable for acid use) 
  • Bucket(plastic) 
  • Stirring instrument (wooden or plastic) 

Test The Water 

The next step is to test the water, blindly pouring chemicals into your pool water without testing it first could be highly detrimental to the health of your pool water. Therefore, always test your water before you start adding chemicals. You need to identify the current pH level by using pH test strips or a digital testing device. 

Work Out How Much Acid is Required 

Before you start adding the muriatic acid to the pool water, you will need to figure out how much water is actually in your pool. If you need to reduce the pH and alkalinity then you can figure out the amount of muriatic acid you would need to reduce the pH more than necessary. Doing it this way should reduce your alkalinity enough to bring it down to normal levels. To bring the pH level to optimum level, switch the pool pump on and aerate the pool to bring the pH level up to the correct point. 

The instructions on the muriatic acid container should give you some idea of how much of the chemical to add, however, there are some online tools available to help you calculate the amount of muriatic acid you should add to the pool water. 

Switch Off the Pump 

To reduce the alkalinity while simultaneously keeping the stability of the pH levels, turn your pump off prior to pouring in the muriatic acid. Keeping the pump facilitates the circulation of the chemicals, it also oxygenates the water. If you want to reduce the alkalinity but keep the pH the same, you want to reduce the amount of movement in the water. Therefore, turning the pump off will help with this. 

Pour The Muriatic Acid into The Water 

Dilute the muriatic acid prior to pouring it into the pool water, doing this reduces the acidity of the acid and makes it safer to use. 10:1 is a good ratio to use for muriatic acid and water, stir using a wooden or plastic stirring instrument. 

Tip: Pour the water into the bucket prior to pouring the muriatic acid into the bucket. 

Now add the muriatic acid and water mixture into the pool, make sure you start from the deepest side. If the pH level is also high and you wish to reduce it, walk around the pool and pour the solution in from different angles. 


Once you have finished using the bucket, wash it out carefully with plenty of water. Use the bucket specifically for muriatic acid, using it for other chemicals could cause a dangerous chemical reaction. 


There are a couple of things you can do here, you can switch on the pump for 30 minutes to boost air circulation to stop the acid from damaging the pool tiles. Or you could wait a bit without using the pump, this is often referred to as “pooling.”  This method might damage your pool tiles therefore, it is often advised to turn the pump on to ease the process. 

Once you have completed the process, you can test the levels and then repeat if necessary. The best way of balancing pH and alkalinity levels using muriatic acid is to do it slowly. 

Pros and Cons of Using Muriatic Acid 

Pros of Using Muriatic Acid to Balance the Alkalinity Levels in Your Pool 

Here is a list of the advantages of using muriatic acid to balance alkalinity and pH levels in pool water:


Muriatic acid is relatively cheap to buy, and it is readily available in most hardware stores. However, it is useful to bear in mind that if you are going to purchase muriatic acid from the hardware store, you must purchase the type that is suitable for use in swimming pool water. 


Muriatic acid effectively balances alkalinity levels in pool water reducing the risk of pool water-related diseases like no virus. 


Cons of using muriatic acid to balance the alkalinity levels in your pool: 

Highly Caustic 

Muriatic acid is highly caustic and it will burn if it comes into contact with your skin. Some pool experts will not recommend that a novice uses muriatic acid to balance the alkalinity levels in their home swimming pool. This is probably best left to the experts. 

Time Consuming

It can be time-consuming if you don’t know exactly what you are doing. To get the right levels, you might have to keep adding and testing for a period of time. 

Muriatic acid is a highly caustic chemical and should be used with caution, and with the correct safety equipment to avoid any accidents taking place. However, it is an effective pH and alkalinity balancer, and managing the pH and alkalinity levels in pool water is vital for the overall health of the swimming pool water. 

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