Lowering pH with Muriatic Acid: How Much Do I Need? [2024]

After buying a pool, its owner will be faced with the issue of proper maintenance. Previously unknown concepts like pH, alkalinity, acidity, and chlorine levels will become part of their life. The longevity of their pool is directly dependent on how effectively it can deal with the problems that arise.

One of the main issues is the high pH level. It can be lowered with muriatic acid. Despite the fact that there are many different ways to lower pH (for example, diluting), we decided to stop at one of the most effective, cheap, and safe method – muriatic acid.

In this article we will tell you why it is important to keep the pH balanced, why high pH is bad, how much muriatic acid you need to add to lower the pH, list the cautions for use, and clarify how to control the pH level.

Why Is It Important To Keep The pH Balanced?

Let’s remember at once what pH is. It is the “hydrogen potential”. What does this have to do with hydrogen? It is an “H” which is one of the main components of water (the water formula is H2O). A small concentration of H in water turns it into an acid, while a large one turns it into heavy water.

Heavy water is water that has a lot of minerals and other particles in it. These can cause scaling and other chemicals to dissolve ineffectively. 

On the chart above, a scale for measuring this pH is shown, where 7 is the average pH that is inherent in distilled water. Anything below 7 is more acidic and anything above that is more alkaline. For a swimming pool, the normal pH is 7.2 to 7.6. 

High acidity turns your water into a corrosive agent for iron and other materials. Accordingly, it is undesirable to bathe in such water, because it can harm your skin as well. High alkalinity makes the water hard because the concentration of minerals in it increases dramatically. This can cause clogs and problems with the water supply.

To reduce the alkalinity, it is worth using muriatic acid. It literally “acidifies” the water and lowers the pH. We explained how muriatic acid interacts with water with a high pH further in the article.

That’s why it pays to keep the pH balance in your pool!

High pH: Why Is It Bad?

Let’s get back to the topic at hand. We are interested in high pH and why it is bad. So let’s first find out what causes the hydrogen concentration in the water to increase:

• A large number of people swimming in the pool at the same time;
• An incorrect filter: If you have a normal pH and you bought a filter for an acidic environment, it will increase the alkalinity;
• Improper use of chemicals.

Now let’s find out in detail what increased alkalinity in the pool water can lead to.

• Cloudy water. It can lead to the accumulation of debris in the filter and rapid wear and tear of the piping system. Also, cloudy water leaves dirty marks on the surfaces with which it comes into contact.

• Scale formation. It clogs filters and heating elements, which can cause them to fail.

• Irritation of the mucous membranes in the eyes. People mistakenly think that chlorine is the main cause of mucosal irritation, but that is not entirely true. The eyes are irritated because of the elevated pH. The pH of the eyes is 7.5. Exceeding this value leads to redness and tearfulness.

• Ineffectiveness of chlorine. Hard water prevents the effective use of chemicals because they do not dissolve in water.

Depending On The Spa Or Pool Volume Of Water And PH Levels

Muriatic acid is used to lower the pH. It reduces the amount of low-soluble salts in the hard water and increases the acidity to balance the pH value. It is important to note that muriatic acid is a cheap method that has its disadvantages. For example, its improper use can harm both the pool and your health.

Before you find out how much muriatic acid you need, you should calculate the volume of the pool or the hot tub and the current pH value. Below we explain in detail how to do it and how these values will affect the amount of muriatic acid to be added.

Depending On The Volume Of Water And pH Levels In The Pool

To know how much muriatic acid you need to add, you should measure the pool volume and its pH level.

The following are formulas for calculating the volume in gallons based on the shape of the pool (in feet).

• Square and rectangular pools (constant and variable depth)

• Circular (constant and variable depth)

• Oval (constant and variable depth)

To calculate the volume of an irregular or kidney-shaped pool you can conditionally divide it into simple shapes (circle, oval, square, or rectangle), calculate the volume of each and summarize.

Next, you should measure the pH level. You can use test strips, a drip DPD test, or an “acid requirement” test for this.

Now you can compare your results to the tables and find out how much muriatic acid you need to add to lower the pH in your pool or in your hot tub.

How Much Muriatic Acid to Add for the Hot Tub’s PH and Its Volume

Expert Tip: Cautions Before Using Muriatic Acid

To lower the pH in pools, people use the muriatic acid with a lower concentration of hydrogen chloride. However, it is still very corrosive and can damage pool finishes, clothing, skin, and cause respiratory tract burns. 

To prevent harm to yourself and your pool, we have compiled a list of must-read cautions before using muriatic acid.

• Keep muriatic acid in the container in which you purchased it. The substance comes in acid-resistant plastic. It is strongly discouraged to pour it into another container because of the possibility of inhaling poisonous fumes. There may also be residues of another chemical in the container that can react with muriatic acid.

• Dilute the muriatic acid with water. Do not add water to a container of acid as it can splash on you. Pour it into a pre-prepared acid-resistant plastic bucket with water.

• Wear protective clothing. Wear rubber gloves, an eye mask, a respirator, and clothing that covers all exposed body parts. Even if acid gets on you, you will have time to get rid of your clothes and avoid chemical burns.

• Keep water and baking soda ready. If acid gets on your exposed skin, you need to rinse the area quickly with water and pour baking soda on the affected area. It will neutralize any acid.

How To Control The pH Level In The Pool?

You can check the pool’s pH level at home. You can buy special kits at any industrial store. There are 3 such test kits and we will tell you about them in detail below.

• Litmus paper. Let the strip into the water for 0.4-0.8 inches for 1-3 seconds. Special scales for comparing readings are supplied in the kit. After measuring, compare your strip to this scale.

• pH meter. Pour the water from the pool into any clean container. Also, the measuring part of the device should be rinsed with distilled water, so that the device is calibrated to the normal pH value. It is enough to take up to 30 ml of pool water. Then the sensor is dipped into the flask with the liquid. The result appears on the screen within 5 seconds after immersion. It determines the pH level with an accuracy of 0.1. 

• Tablets. You need to put it in the water. After it dissolves, a spot of a certain color will appear. Depending on its color, we can determine the pH level.

Summary

A high pH level is harmful to the pool and the people who swim in it. It can cause limescale to form, which will clog filters and heaters, appear cloudy water, which will breed bacteria, and so on.

High pH levels in the pool can be effectively dealt with by using muriatic acid. It lowers the alkalinity of the heavy water to a perfect pH of 7.2 to 7.6. However, it is important to use muriatic acid carefully so it does not harm your pool or your health.

In this article, we’ve listed why you should balance the pH, why high pH is bad, how much more muriatic acid you should add depending on the pool water volume and the current pH, the cautions for using muriatic acid, and how to control the pH.

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