What Does Muriatic Acid Do for a Pool?

This article will provide you with information on the uses of muriatic acid for pool and balancing the levels of pH and alkalinity.
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Last updated: August 25, 2023
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The chemistry of your pool water is key if you want to keep your pool usable and enjoyable all season long. You will have to balance the alkalinity, the pH, the chlorine, and the calcium hardness to be able to make your pool water ideal for use. This can be a complex process without the right tools on hand to keep your pool water at its peak quality.

Muriatic acid for pool can be a very useful tool when you are working to maintain pH, and knowing how to use this tool is critical for the best results. Like many of the various tools that can be used to balance pH and water quality, muriatic acid for pool management can make your water-balancing process much easier and more efficient. If you have never heard of muriatic acid and what it can do for your pool water, you need to keep reading for more information.

What is Muriatic Acid?

What Does Muriatic Acid Do for a Pool?
Muriatic acid itself is a diluted version of hydrochloric acid that is used for intense cleaning tasks

If you have been wondering what muriatic acid is used for in a pool, you need to know what this substance is first and foremost. Muriatic acid is a diluted solution of hydrochloric acid. It is sold at many home improvement store locations, but you can also get it from pool supply stores. It is intended to be used for intense cleaning tasks such as removing salt deposits or rust and stains from various surfaces.

Muriatic acid might be a component in various pre-prepared pool pH products, or you can add it to your pool alongside other chemicals that you add one at a time. Many people use muriatic acid as just one of the various components that are part of their pool management process. Since it is primarily used for acid reduction, you might only need to use this substance for instances when your pool’s pH is off. However, when you choose to purchase it by itself, you can also use it to clean pool surfaces and toclean the filters that you use for your pool as well.

What Is It Used for in a Pool?

There are various uses that you can apply muriatic acid for when taking care of your pool water. You might want to use it for any of these reasons throughout the seasons of management that are necessary for a pool. If you have been looking into what muriatic acid can do for your swimming pool, these are the primary things that it is used for:

Lowers Alkalinity and pH levels

What Does Muriatic Acid Do for a Pool?
The main reason of adding muriatic acid to your pool is balancing the pH of your water

This is the primary reason that you will want to use muriatic acid for your regular pool management needs. You will need to know how to properly dilute muriatic acid for this kind of pool use, but once you are familiar with this process, you can balance the pH of your pool water correctly with its help. If you are wondering how much muriatic acid for a 5,000 gallon pool, you need to start with a pool water pH test. The muriatic acid container should tell you how much acid to add per gallon of water, and your pH test will tell you how much the pH needs to be altered to make the balance correct.

Making sure to dilute your muriatic acid solution properly is critical for the best results when utilizing this substance to balance your pool’s pH. Make sure that you read the instructions for your muriatic acid product carefully and that you take care to be sure of the pH that you are starting with in your pool.

Cleans Filters

What Does Muriatic Acid Do for a Pool?
Muriatic acid can also be used as a cleaning tool for variety of surfaces

Muriatic acid can also be used to clean a variety of surfaces because it is naturally so caustic. You can easily remove rust, stains, and debris from your filters by soaking them in a bucket that is filled with a solution of muriatic acid. Be sure that you do not splash this substance on your skin or clothing as you are placing the filters in the solution or taking them out when they are done soaking. Muriatic acid can cause mild skin irritation and burns.

You will want to rinse your filters carefully when they are done with their soak to make sure that you do not impact the pH of your pool water when you reinstall your filters. Make sure to wear gloves and rinse your filters so that animals and other people cannot be impacted by the acid as it is removed from the filters. When diluted into the pool water properly, this substance is not harmful, but when used for cleaning purposes, it can be quite caustic and might cause burns.

Removes Pool Surface Stains

What Does Muriatic Acid Do for a Pool?
Muriatic acid can help your pool to look brand new with its stain-cleaning capabilities

Just like in the case of cleaning your pool filters, you can clean pool surface stains with muriatic acid as well. Make sure again that you do not splash the substance on your skin or clothing, and wash the surface that you have cleaned thoroughly when you are done with your soak. You might need to leave the acid for part of a day, so be sure that children and animals do not interact with the soaking area until the muriatic acid has been removed completely.

Being able to make your pool area stain-free can help make your pool look new again and can also greatly improve the appearance of a pool that has aged somewhat or been stained related to winter conditions or being drained for too long. The best above-ground saltwater pools can also necessitate this kind of clean-up from time to time due to the residue that can be left behind by salt water after some years of use. Water that has not been maintained with the proper usage of the best pool chlorine tablets can also cause stains to crop up in your pool.

Safety Precautions

What Does Muriatic Acid Do for a Pool?
Wearing googles, gloves and protective footweat is necessary when working with muriatic acid

Due to the highly caustic nature of undiluted muriatic acid, you will need to wear goggles, gloves, and protective footwear when you are using this substance to clean filters or remove stains from surfaces in or around the pool. Make sure that children and pets are not interacting with undiluted Muriatic Acid to reduce the chance of poisoning or burns.

If someone in your household has come into contact with undiluted muriatic acid, make sure to rinse the area with cool water right away. If the acid has gotten into someone’s eyes, flush the eyes immediately with cool water and attempt to rinse for at least 15 minutes. Make sure that you seek medical evaluation as soon as possible after any contact with muriatic acid that involves the eyes or other sensitive tissues.

Contact poison control immediately for any situation where muriatic acid has been ingested. The sooner that someone who has ingested muriatic acid receives medical attention, the better. Muriatic acid can be quite safe to use for your pool maintenance, but only when it is managed responsibly and put away carefully when not in use. This is true of almost all your average pool chemicals, and you need to be sure that you are not leaving these substances out in the open for children and pets to get into with ease.

How to Lower Alkalinity and pH with Muriatic Acid

The pH of your pool water can be impacted by rainfall, outside temperatures, and the frequency of use of your pool. You will want your pool water to be between a pH of 7.2 and 7.8. If the pH is above this range, it is too soft and is not acidic enough. If the level is below this range, then the water is too hard and too acidic. When the water in your pool does not have the right pH, it can feel unpleasant, smell bad, or even look dirty.

Another sign that your pool water pH is not correct are stains and salt lines around the edge of the pool. These can be hard to remove without the help of muriatic acid and can make your pool look old and poorly cared for. When you see these warning signs of pH issues, you can use muriatic acid to help balance your pool’s pH right off and control large swings in the pH that are hard to correct for.

Test Your Pool WaterWhat Does Muriatic Acid Do for a Pool?

Testing the pool water is important to know what the pH needs to be. Pool water testing kits are a must when you have a pool that you are trying to manage. The best pool test kits are specifically designed for the management of pool water and can make all the difference in your weekly care for your pool. Most of these kits will be marked for the ideal pool water hardness, alkalinity, and pH so that you do not have to worry about forgetting what these numbers should be.

Testing kits often offer great advice on how to use them, and most pool stores or pool sales locations will be happy to show you how to test your water correctly. Take advantage of this training as needed to be sure that you are getting the right pH readings for your pool management needs.

Once you know what your pool water pH is, you will need to turn off your pool pump before you start making adjustments to the pH and other water values. Be sure that you have tested accurately, and double-check your numbers if you are in doubt. Adjusting the pH incorrectly because of improper water testing can lead to bigger struggles trying to make the water balance properly.

Determine the Required Amount of Muriatic Acid

The amount of muriatic acid that is needed for your pool will depend on the pH reading that you have discovered when you were testing the water. You will need to mix your muriatic acid solution carefully in a bucket that is safe for use with acid products. Make sure that you pour slowly to avoid splashing and that you wear safety items like goggles and gloves when you are mixing.

The amount of muriatic acid that needs to be added to balance the pH will have a lot to do with the size of your pool. You will need to know how many gallons your pool is to be able to create the right muriatic acid mix. Overall, per 10,000 gallons of water, 10 oz of 15% strength muriatic acid will lower the pH by about 0.1 and 1.6 ppm. The numbers might be slightly different depending on the pH and alkalinity of the water when you start making adjustments.

Dilute the Acid

The acid will need to be diluted carefully and completely. Make sure that you refer to the bottle to create the right percentage solution for your needs. Stir carefully to prevent spilling and splashing, and make sure that you are not doing this process near children or pets. You will want to be positive that you are not going to get the solution on your skin to prevent burns, and you should clean up spills carefully to prevent issues with contact with puddles of the partially diluted acid.

Do not add water to the acid as you are diluting it. This can lead to a chemical reaction that causes the water to spray out of the bucket and burn you. You should put the water you need into the bucket first and then mix the muriatic acid into the bucket with a 1/10 ration of acid/water. Make sure as well that you use clean water and not water that you have scooped from the pool.

Add Muriatic Acid to the Pool

What Does Muriatic Acid Do for a Pool?Pour the acid dilution that you have created into the pool slowly and carefully and then mix it around with an acid-safe stirring stick. You will want to be sure again that no children or pets can contact the water while you are working on this step. Until the muriatic acid solution has been diluted into the pool water completely, it could still burn someone or get in their eyes and cause injury.

Always clean your mixing bucket thoroughly after you have added acid to the pool. The acid that remains in the bucket can impact your dilution for your next addition to the pool, and it can also cause damage to the bucket that might ruin it. Make sure that this bucket is used only for this process ad muriatic acid can impact other pool chemicals negatively and it can pose a health risk when mixed with some other substances as well.

Turn the Pool on

Turn your pool pump back on and let the water circulate for a few hours. You will want to wait at least one hour, but waiting for two or three is a better idea. Be sure that the filters are clean and that the pump is running efficiently as well before you trust that your muriatic acid solution has completely mixed into the pool water.

When the pump is running, the pool water will aerate slightly, which will also change the pH. Make sure that you are not testing too long after you have turned off the pump for this reason as well. The pool water will need some time to fully aerate, and it will not immediately lose this quality when you turn off the pump, but if you wait to test for an hour or more, you might not be getting an accurate pH for your testing needs.

Test and Repeat if Needed

What Does Muriatic Acid Do for a Pool?After the muriatic acid has been allowed to mix into the pool water for a few hours, turn the pump off again and test again. You will want to see if the pH has come down to the right levels and check the alkalinity and the hardness. You might not need to add any more pH adjustors if you are still struggling with the other factors of the water. If the pH is still way off, take your new pH level and use it to calculate the amount of muriatic acid to add for a second round of balancing. This can happen when pool water has not been treated in some time or when bringing the pool out of a winterized status. Be sure that you are testing carefully and patiently so that you know that you are getting the right results for your efforts.


Can I use muriatic acid for salt water pool?

This is one of the key pool types that need muriatic acid to be correctly balanced. You will want to be sure that you take into consideration the pH needs of your saltwater pool when adding this acid to it, but you will often get great results from balancing this kind of pool with muriatic acid.

How long does it take for muriatic acid to work in a pool?

It will take about 24 hours to see the full effect of the muriatic acid on your pool’s pH. This is why it is so important to wait some time after adding the acid to test your pH again and to move the needle on the pH number slowly. It can be easy to overcompensate and cause a situation where your pool’s pH is incorrect in the other direction due to the addition of too much muriatic acid to the pool water.

What happens if I put too much muriatic acid in my pool?

If you add too much muriatic acid to your pool and the pH drops below the optimum level, you will need to add sodium carbonate or soda ash to correct the imbalance. You can go back and forth like this when you test too soon after adding muriatic acid, which is why it is a good idea to be sure to hold off on retesting for a while to allow the chemicals to circulate in your pool for a bit.

How soon can I use the pool after adding muriatic acid?

You will need to wait for at least 30 minutes before you swim in the pool. It is best to wait at least until the next day to swim in the pool just to be safe, but you can probably get away with waiting a half hour or an hour before you swim. If you have used the muriatic acid to clean the pool surfaces, make sure that you rinse the area thoroughly and not into the pool to make sure that the surfaces and the pool water are safe for use again.

Are there other substances you can use instead of muriatic acid?

You can also use pool algicides for this need, and you might also be able to replace the muriatic acid with sodium bisulfate, or sodium dichlor and trichlor. These other chemicals require their own processes to be added safely to your pool and cannot be added in the way described in this article for muriatic acid.

Will muriatic acid clear a green pool?

Muriatic acid can be part of the solution to clearing a pool that has grown algae. There are many steps to this process, including a thorough cleaning and vacuuming process, but you can use muriatic acid per manufacturer instructions as part of the solution for this kind of pool problem. Pool bleach might need to be used alongside muriatic acid to clean up algae, and you should use both with the expectation that your pool will not be useable during the cleaning process.

How often should I add muriatic acid to my pool?

Muriatic acid should be added any time that you need to balance your pool’s pH. When added weekly or as needed to balance pH, you will be less likely to have to worry about huge swings in your pool’s pH levels. Larger shifts in pH are much harder to manage overall, so you do not want to allow your pool water to get very far outside of the optimal range before you attempt to correct it.

Are saltwater pools easier to maintain?

Saltwater pools can be much easier to maintain overall and often require fewer chemicals to be useable at all times. You will find that the water in a saltwater pool is often softer on the skin and smells better. This is also a great choice for those who are allergic to chlorine.

Final Thoughts

Muriatic acid for pool is a powerful chemical that can be used for cleaning filters, lowering pH and alkalinity, and removing stains. However, it is also important to be aware of the potential dangers of using this chemical. Make sure to follow all safety precautions when using muriatic acid, and always store it in a safe place away from children and pets.

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