How to Use Muriatic Acid in Pools and Spas

One way to keep the pH balance in your pool at the correct level is by using muriatic acid. While this type of acid, also known as hydrochloric acid, can be dangerous, it’s a welcome addition when treating your pool water, provided that you do it correctly and under the right circumstances. Fortunately, both determining whether your pool needs more acid and the process of adding the muriatic acid are easy to do. By following these steps, you can keep your pool in good working order with minimal effort.

Step 1 - Testing the Pool

It is possible that your pool does not need muriatic acid at all. However, to be sure that it is or is not necessary, you should get your pool water tested. This will tell you the pH balance in your pool water and let you accurately what amount of muriatic acid you need to add to keep it at a good level.

Get a bottle and fill it with water from your pool or spa. Next, take that sample to professionals for analysis. Any store that sells supplies for your pool will be able to either do this themselves or direct you to a service that can. Once you have the results back, you can use them to decide what to do next.

You can also decide to use your own pool testing kit if you prefer.

If the results show that your water has an appropriate pH value, you are done. Continue to test regularly, as you will likely need to add acid eventually.

Step 2 - Preparing the Acid

If the test results determine you need to raise the acidity of your pool water, begin by filling a bucket with clean water, not pool water. Be sure to take note of approximately how much water you have added to the bucket. Next, add muriatic acid to the bucket. Never use more than one pint, and never use more than 1/10 of the amount of water you've already added.

Be extremely careful when handling muriatic acid as it can burn skin and damage clothes. Wear protective gloves, clothing, and eye protection if necessary.

Step 3 - Adding the Acid

Ensure that your pool’s filter is turned on and begin adding the mixture of water and acid to the pool. Do this in stages so that you make a complete circle around your pool, adding small amounts of the diluted acid spread evenly around the areas as you pass them. Dumping the entire bucket in at one spot will make the distribution uneven.

If you are adding muriatic acid to a spa, still do your best to broadcast the mixture throughout the entire spa. However, it is not as crucial here since factors like the smaller space, running filter, and potential to use jets to agitate the mixture will all likely spread the acid just as well.

Finish up by adding the remainder to the deep end. Do not use your pool for at least 30 minutes.

Step 4 - Maintaining the Balance

Once four hours have passed since adding acid to your pool, take another sample of the water. Have this sample tested, or test it yourself. When you have the results, you may want to add more acid. However, adding more acid before you have the test results is a bad idea. Test your pool or spa regularly.