Everything You Need To Know About Muriatic Acid In Your Pool


You’ve probably figured out by now that it takes more than chlorine to keep a pool safe and clean.

Even though the big “C” gets all the glory, it has some pretty hefty sidekicks backing up its work.

One of those is muriatic acid. 

In this guide, we go everything you need to know as a pool owner about muriatic acid.

What is muriatic acid?


Muriatic acid is “a less-pure variant of hydrochloric acid.”

It’s an extremely caustic and corrosive substance that should be handled carefully, but it’s very effective in balancing pH levels in water. 

Aside from that, it’s also used to clean tiles, remove rust stains, dissolve calcium deposits, kill mold, and clean pool surfaces.

So, not only can you add the stuff to your water to keep it balanced, you can also use it to scrub your pool surfaces to keep them sparkly clean.

Why should you add muriatic acid to your pool?

When your pool’s pH levels climb a little too high (usually, anything above 7.8), the water is considered to be too alkaline, or too basic. (Read: how to lower alkalinity in your pool).

Water that’s too alkaline can cause all kinds of problems for your pool, including scaling, chlorine inefficiency and cloudy water.

Scaling may sound harmless, but those calcium deposits can actually harm your plumbing and equipment. 

Also, as you probably already know, when any level is out of whack, it tends to throw off the others. 

Muriatic acid and sodium bisulfate are the chemicals you can use to lower your pH levels.

How to use muriatic acid for your pool

Step 1. Test your pool levels

First of all, you need to test your pool’s chemistry

Use your pool test kit or strips to find out if the pH levels are in balance.

If they are in fact too high, you’ll need to break out the muriatic acid.

Step 2. Wear protective gear

Always wear protective gloves and eyewear when using muriatic acid.

It’s also best to wear clothing that covers your arms and legs in case of splashing; if your skin does come into contact with the acid, run cool water over the area immediately to remove it.

Step 3. Dilute the acid

Fill a five-gallon bucket with clean water (not pool water).

Next, add about 1/10th as much muriatic acid as water to the bucket.

Step 4. Add the acid to the water

Turn on the pool pump and slowly add the acid and water mixture all the way around the pool’s perimeter.

Do not re-enter the pool for at least half an hour. 

Step 5. Check the pH levels again

After a few hours, test the pH level again.

If the pH levels are still too high, you may add a little more muriatic acid.

Continue to test every 4 hours until the levels are at optimum range (7.2-7.8).

Muriatic acid vs. sodium bisulfate

Another popular pH decreaser is sodium bisulfate. In fact, a lot of the products you can buy on the market will contain this.

And it’s a good alternative to muriatic acid for a couple of reasons.

For one thing, it’s much safer to handle and to store than muriatic acid. It’s also easier to use because it won’t cause pool damage or burn your skin if it is accidentally spilled.

So, why would anyone choose muriatic acid, then? 

Well, quite simply, it just does the job a lot faster.

Where muriatic acid will usually reach its potential in 3-4 hours, you won’t be able to tell if sodium bisulfate has done its job for at least 24.

And even though sodium bisulfate is less caustic, it’s still important to use it carefully.

Bottom line

The main use for muriatic acid in a pool is to lower pH balance.

But it’s also a great chemical to have on hand for heavy duty scrubbing when scaling and calcium deposits are a problem.

The main thing to remember is to use extreme caution when handling and storing this chemical.

Keep it out of the reach of children and pets in a cool, dry area!

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