What does Muriatic Acid do for a Pool? What is Muriatic Acid? Why pH Matters Muriatic Acid: pH Reducer Other Ways to Use How to Use Muriatic Acid Final Thoughts

What does Muriatic Acid do for a Pool?

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Muriatic Acid: A Guide for Swimming Pool Owners

Chemistry is a huge part of swimming pool maintenance: Balancing your alkalinity, pH, chlorine, and calcium hardness is essential to keeping a pool in good shape.

There are several different products that can help you accomplish this task including Muriatic Acid. In this article, we’ll take a deep dive into the ways muriatic acid can help manage your pool such as reducing pH levels and cleaning cartridge filters.

What is Muriatic Acid?

Muriatic acid is a diluted solution of hydrochloric acid. You can buy it at most home improvement stores, and it’s used for a variety of heavy-duty tasks, such as removing “efflorescence” (a fancy word for salt deposits on rock or stucco). It’s also used to remove rust and stain from concrete and brick.

And, of course, muriatic acid is also a big seller at pool supply stores, where it’s often used as a stain remover. It’s also used to reduce high alkalinity or and lower the pH in pool water.

Did You Know?

Your stomach naturally produces muriatic acid to help you digest food and break down potentially harmful bacteria.

Why Your Pool’s pH Matters: And How Muriatic Acid Can Help

pH is a measure of how acidic your pool water is. Things that can affect your pool’s pH include rainfall, outside temperature, and how often your pool is used.

Ideally, you want your pH to be somewhere between 7.2 and 7.8. If your pH is below 7.2, it’s too acidic. If your water is above 7.8, it’s not acidic enough. When your pool has high pH/low acidity, chlorine is less effective, your pool water can become cloudy, and you may notice scaling on your waterline tiles and other surfaces.

The quickest way to get your pH back to an acceptable level is to use a chemical pH reducer. Pool supply stores sell muriatic acid or sodium bisulfate as pH reducers. Sodium bisulfate, or dry acid, comes in a powder form and is more mild than muriatic acid, so it’s a little safer to use, but many pool owners use generic muriatic acid as a substitute for pH reducers.

Using Muriatic Acid as a pH Reducer

First things first: You need to know how much muriatic acid to use. For an average-sized pool (think 15,000 to 20,000 gallons), you’ll need about a quart of muriatic acid. If your pool is much larger or much smaller than average, you should check with your pool professional.

Once you know how much acid you need, it’s time to add it to your swimming pool. Here’s how to do it:

Step 1: Test and prepare

Start by testing your pool water, so you know exactly what your pH is. Then, turn off your pool pump.

Step 2: Mix the solution

Fill a five-gallon bucket with clean water (you’ll want to make sure the bucket is safe to use with muriatic acid – it can be too harsh for some types of plastic). Add the muriatic acid to the water (be sure to pour slowly to avoid splashing) and stir carefully with a wooden stick.

Safety First!

Although you can technically pour muriatic acid directly into your swimming pool, diluting it with water first makes it a little safer to work with.

Step 3: Add the acid

Slowly pour the mixture into the deep end of your pool, and wait a few minutes for the solution to disperse. Wait a few minutes, then turn on your pool pump so the muriatic acid can circulate through your pool’s filtration system.

Step 4: Test again

Wait a few hours and test your swimming pool water again. If the pH is back within an acceptable range, you’re good to go. If your pH is still too high, you’ll need to go back to step one and repeat the process.

Other Ways Pool Owners Can Use Muriatic Acid

Muriatic acid isn’t just helpful as a pH reducer: It’s super-helpful for cleaning cartridge filters (it breaks down buildup in a snap). It’s also a powerful stain remover: Muriatic acid can take rust stains off of your pool’s surfaces, and it can even clean the grout between your swimming pool tile.

Pro Tip

Muriatic acid works well for removing stains on gunite pools, but it’s too harsh for vinyl liners. Instead, look for a cleanser that’s specially formulated for vinyl pools.

Of course, whether you’re using it to balance your pool water or keep your swimming pool free of stains, the most important thing to remember about muriatic acid is safety.

How to (Safely) Use Muriatic Acid

Is muriatic acid dangerous? Like any other swimming pool chemical, it can be harmful if not used as directed. But as long as you follow proper safety procedures, there’s nothing to worry about.

Here are a few tips for staying safe when working with muriatic acid:

  • When you’re working around your swimming pool, splashing is always a risk – a good pair of safety goggles is a must-have.
  • Like any strong acid, muriatic acid can irritate your skin (prolonged exposure can even cause burns). Gloves will help you avoid direct contact.
  • If you do get muriatic acid on your skin, wash the area with clean water right away (it’s a good idea to keep a garden hose or a bucket of clean water nearby).
  • Use muriatic acid in a well-ventilated area and avoid breathing fumes.
  • Always store muriatic acid in its original container.
  • Don’t pour unused muriatic acid in the drain. Check with your local recycling center to find out how to dispose of it properly.

Final Thoughts: Muriatic Acid Keeping Things Balanced

When it comes to swimming pool maintenance, muriatic acid keeps your water balanced and your chemistry in check. And when everything is in balance, you’ll spend less time scrubbing algae -- and you’ll have more time to enjoy your pool.

Of course, remember to use it carefully and follow all safety precautions. And if you have any questions or concerns, talk to your local pool professional.