How to Use Muriatic Acid to Lower Your Pool’s Alkalinity

A swimming pool can be the most valuable amenity in the house as long as you are maintaining it the right way. Taking care of the landscape around the pool, changing its filtration/circulation system, and most importantly, taking care of pool chemistry are some of the essential features of a good pool maintenance regimen.

If we mainly talk about pool chemistry, then the alkalinity of the pool water seems to be a significant pain point for owners. High alkalinity indicates a high concentration of carbonates and bicarbonates (calcium) in the pool. These alkaline chemicals pose a threat to the circulation and filtration system of the pool. Also, highly alkaline water provides a suitable breeding ground for algae.

Muriatic Acid Is the Answer

Alkalinity levels in the pools usually fluctuate. However, if you notice the levels are continually going up while also causing some noticeable side effects, you can take a proactive approach to take care of it.

You can use muriatic acid to lower the alkalinity and, thus, the pH level of the water. pH indicates the level of acidity or alkalinity of the water with a scale from 1 to 14. pH score of 1 means highly acidic and 14 means highly alkaline. A score of 7 indicates a neutral medium that is neither acidic nor basic.

In its muriatic form, hydrochloric acid is known as muriatic acid. Commercial muriatic acids for swimming pools are HCLs that have been diluted to a pH of about 2. Muriatic acid has a low pH, which neutralizes the high pH of the alkaline water medium when dissolved in it.

However, reducing pool alkalinity with muriatic acid is more complicated than it may seem. Given that you are working with an acid, it is imperative that you exercise caution when applying it to the pool. It’s important to maintain a healthy alkalinity level and avoid reducing it too much.

Both low and excessive alkalinity levels are bad for your pool, and we’ll explain why in the following sections. We will also document the process of employing muriatic acid to remedy the high alkalinity of pool water.

Recommended Alkalinity Level for Pools

By now, it is clear that alkalinity is the opposite of acidity. In other words, the presence of alkaline substances in the water (carbonates, bicarbonates, hydroxides) acts as a buffer that ensures pool water doesn’t turn acidic.

Experts recommend any alkalinity level between 80 and 120 parts per million (ppm) is suitable for a pool. It ensures pool water doesn’t turn acidic and doesn’t face scaling and calcium buildups either.

See also: Top 7 Pool Pumps With Reviews

The Dynamics of Alkalinity in Pool Water

When the pool water has a recommended level of total alkalinity (80-120 ppm), the pH scale records the value somewhere around 7.4-7.6, which is slightly alkaline. So, why do we need our pools to be somewhat alkaline? Chlorine, the primary pool water sanitizer, works best in a slightly alkaline medium. Also, these levels of alkalinity remain inert for the pool and the people who are using it.

What Happens When Alkalinity Levels Go Low?

When total alkalinity levels fall below 80 ppm, the pool water turns acidic. The high acidic levels don’t pose any extreme threat to the well-being of pool users and the pool itself. Nonetheless, it can lead to these unwanted outcomes.

  • Eye and skin itching and burning
  • Staining, etching, and corroding of pool equipment and surface
  • Pool water getting a slight tinge of green

Related: How to Clear a Green Pool in 5 Days

What Happens When Alkalinity Levels Go Up?

When the alkalinity level shoots through 120 ppm, your pool water becomes an alkaline/basic medium, and that is not good due to the following reasons.

  • Clogging of pool equipment and scaling of pool surface
  • Burning sensation and rashes on the skin
  • Pool water develops a slightly gray tinge

What Causes Alkalinity Levels to Go Down?

Bodily fluids (urine, sweat) can drop the alkalinity and pH levels of the pool water. Apart from that, rainwater can also drive the alkalinity of the pool down.

What Causes Alkalinity Levels to Go Up?

The source of water you are using to fill your pool is the primary reason for increasing the alkalinity levels since it already has a high level of calcium and other basic/alkaline elements in it. Body lotions, sunscreens, and even chlorine-based pool shocks raise the pool’s alkalinity levels.

How to Use Muriatic Acid to Decrease Pool Alkalinity?

You may have seen off-the-rack products in pool stores that are labeled as “pH Decreasers.” They are primarily made for dealing with pool alkalinity. However, they are more expensive than a regular muriatic acid supply you will need. Also, the rightly done muriatic acid treatment is more effective and produces lasting results.

Let’s look at the steps one needs to follow for using muriatic acid in the pool. Besides muriatic acid, you will need the following items as well.

  • Acid-resistant gloves
  • Safety goggles
  • Chemical-resistant apron
  • A non-metallic bucket (preferably plastic)
  • Plastic or wooden stirrer

Here are some top-quality and reasonably-priced recommendations for the items mentioned above that you can easily find online.

  • Showa Atlas 772 M Nitrile Elbow Length Chemical Resistant Gloves: These Elbow-length chemical resistant gloves are an excellent value for money. They offer optimal safety to your hands and arms during the use of muriatic acid or any other strong chemical. They are made of nitrile instead of PVC and free of uncomfortable seams. They also offer better dexterity than regular acid-resistant gloves.
  • MCR Safety Glasses with Non-Slip Hybrid Black Temple Sleeve: Muriatic acid, even in the diluted form is quite caustic. The fumes emitted out of the muriatic acid solution can cause eye irritation. These safety goggles by MCR Safety are good to ensure eye and face safety while handling muriatic acid. They are made of rugged polycarbonate frames and lenses but feature a gel-filled nose-piece to ensure convenient use. The price point is also quite low.
  • Aulett Home Waterproof Rubber Vinyl Apron: The use of an apron will protect your clothes and skin from any exposure to the muriatic acid solution. This Aulett Home apron is a multipurpose item. Besides using it during muriatic acid treatment of the pool, you can wear it during a host of household works that involve strong chemicals.
  • Encore Plastics 5-Gallon Mix ‘N Measure Plastic Pail: Instead of using any existing tub or bucket for the mixing of muriatic acid, get a new one instead. This pail by Encore Plastics can be a good option. This 5-gallon bucket features a measuring scale, flat bottom for easy mixing, and a handle with a foam grip for smooth movement.

It is highly recommended to work with the above-discussed or other similar items when you want to use muriatic acid in your pool. Nothing is more important than personal safety. Also, buying these items is not an expensive affair. All this safety gear is a one-time buy and won’t cost you more than $50.

Water Testing

Once you are ready with your safety gear, it is time to test the pool water for its pH and total alkalinity levels. Even if you can tell that pool water is alkaline just by looking at its color and scaling, it is still necessary to get an empirical value of the alkalinity. It allows you to establish the quantity of muriatic acid that has to be added to the pool to lower the pH level but without dropping it below the recommended level.

There are two ways you can test the alkalinity of pool water.

  • Test strips
  • Digital test kits

Test strips offer a cheap and effective way to test your pool for its chemistry. From total alkalinity to free chlorine and hardness, they measure a list of chemical compositions in the water. AquaChek Select 7-IN-1 Pool and Spa Test Strips Complete Kit is a good option for testing your pool water for its alkalinity. While you are at it, you can also find out the chlorine levels of the pool to know when to schedule the next shocking job.

If you don’t want to put up with the slow results of test strips and also want to know the exact number instead of analyzing the changing colors of strips to determine the value, you can opt for a digital pool water test kit. They also offer the same chemical analysis as strips. However, they use a photometer that produces a quick digital reading of test results.

Related: Top 7 Pool Test Kits in 2023

Adding Muriatic Acid to the Pool Water

It is a tricky bit, and this is where you need to exercise due diligence to make sure you don’t add too much acid to the water. Experts recommend pool owners keep the addition of muriatic acid into the pool water slow. You can, however, follow some values to start the process.

For instance, if you have a standard 15,000-gallon inground pool that is showing alkalinity levels around 7.8-8.0 pH, you need to add a quart (a quarter of a gallon) of muriatic acid to the pool and let the pool aerate and circulate for up to an hour. Test the water afterward; if you notice a significant pH drop, you have added the right amount. Otherwise, add some more muriatic acid. However, you need to proportionate it with the remaining total alkalinity level you need to drop. For above-ground pools, it is always better to start with a cup of muriatic acid.

Keep in mind that it is better to introduce smaller amounts of muriatic acid in the pool in multiple steps instead of adding all of it at once. This way, you can avoid adding too much muriatic acid in the pool. The addition of excessive muriatic acid in the pool can cause the following problems.

  • It will eat away the metallic and concrete parts of the pool
  • The etching caused by excessive acid exposure can mess up the pebble finishing of the pool by loosening the plaster holding them together.

Add After Dilution

It is better to dilute the muriatic acid before adding it to the pool. You can undoubtedly add muriatic acid directly to the pool, but it entails a splashing hazard. Also, sudden exposure of concentrated acid can damage some of the pool’s features even if it is for a couple of seconds. This is the reason we have recommended you in the previous section to get a plastic bucket in which you can make the diluted muriatic acid mixture without posing any threat to yourself and the pool.

The effective yet harmless muriatic acid water solution has a ratio of 10:1 (one part of the acid with ten parts of water). So, if you are adding a quart of muriatic acid to the pool, mix it with the 10 quarts of water, gently stir it, and then pour it into the pool.

Additional Considerations to Make

You can use muriatic acid to give you several different results concerning total alkalinity and pH levels.

Lowering Total Alkalinity without Lowering the pH

It is important to understand that the pH score doesn’t reflect the level of total alkalinity. If you want to get the total alkalinity levels down by a significant margin but without disturbing the pH levels too much, turn off the pool pump before the addition of the muriatic acid. Pumping entails bubbling and churning, where a lot of oxygen is added to the pool water. The presence of oxygen increases the effects of muriatic acid on the pH levels.

However, you also need to make sure that the acid doesn’t sit at the pool’s bottom to damage its floor. Therefore, after half an hour, when muriatic acid has done a big chunk of its work, open the pump. This way, you can manage to: lower the total alkalinity, maintain the pH level, and protect your pool surface from getting damaged.

See also: Top Picks for Pool Chlorine Tablets

Increasing the pH

If you think you have added slightly more muriatic acid that might increase the pH score beyond recommended levels, aerate your pool for some time. You can use the jets of your pump and circulation system. Move their heads above and set the pump at its highest setting and let it run for a couple of minutes.

The other way to aerate the pool is to use a water feature/fountain. Poolmaster Swimming Pool Waterfall Fountain is a reasonably-priced pool item that you can use for aeration. It is easy to install and offers a high water jet that doesn’t just help you in increasing the pH of the pool but can add more fun to the pool.

Related: Most Recommended Pool Safety Fences in 2023


At first, lowering the alkalinity of the pool with muriatic acid may look like a daunting task. However, if you don’t rush into it, follow the steps and incorporate the previous results to the next cycle, you can easily lower the alkalinity to the desired levels.

Protect your pool from staining, corrosion, and algae growth by keeping the alkalinity and pH levels stable. A better job of chlorination can be achieved by monitoring the alkalinity levels of the pool water.

It is essential to keep the pool’s chemistry balanced to ensure a safe and enjoyable swimming experience. It also aids in maintaining the pool’s functionality for a longer period of time. And you can’t accomplish that if your pool’s alkalinity is out of whack.

Related: 7 Recommended Above Ground Pools in 2023

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