Can I Add Muriatic Acid All at Once? | How to Safely Add

So you’ve just done a pH test and your water is too alkaline. You know you need to get that pH down before it damages the filtration system, or becomes a safety risk, and you’ve heard that muriatic acid is a great way to do that. But how? Can you just add it all at once? Do you need to wait before or after adding chlorine?

In this post, we’ll set the record straight and answer all these questions for you. We’ll give you some safety tips to make sure that your pool isn’t damaged and you’re not risking your safety or the health of your family by making mistakes.

chemical-added-to-pool
Safely adding chemicals to pool.

Can I Add Muriatic Acid All at Once?

It’s best to not add muriatic acid all at the one time. You want to take it slowly when adding muriatic acid into your pool and dilute it first in a bucket. This way, you can add the acid safely and gradually.

There’s a lot of bad advice online that claims it’s okay to pour muriatic acid (aka hydrochloric acid – HCL) straight out the bottle as long as you walk around your pool while you’re doing it, but this is terrible advice. You should always dilute your acid first. This way you can add it gradually and test your pH as you do so to make sure you’re not adding too much.

How Much Muriatic Acid Can You Add at One Time?

Usually 2 cups of muriatic acid in a 24 hour period is safe to add to a pool at the one time. Factors determining how much acid to add are how strong the muriatic acid is and the volume of your pool.

The stronger the muriatic acid (aka Hydrochloric Acid) is, the less you can add at once. In a 10,000 – 15,000 gallon pool, you should not add more than 2 or 3 cups of muriatic acid in a 24 hour period.

What Happens if I Add Muriatic Acid All at Once?

You should avoid adding too much muriatic acid all at once. If you do, the pH levels in your pool water could be dangerously low and cause rashes and eye irritation. Low pH levels can also corrode metals like ladders, railings, screws, bolts, and other important equipment in your pool.

How to Safely Add Muriatic Acid to a Pool

Before you add any chemicals you want to test the water to make sure you really need to. To test the water, you can use test strips, a quality liquid test kit or you can take a sample of your water to a local pool store.

Next, you need to work out how much muriatic acid to add to your pool. More on that in the “How Much Muriatic Acid is Needed” section.

To add the muriatic acid safely you need to dilute the acid into a bucket of water.

To do this safely, wear chemical resistant gloves and a chemical-resistant apron and goggles if you have them.

Then add 1 part of muriatic acid to 10 parts of water in the bucket. Add the water first, then add the muriatic acid. Do water first then acid to avoid splashing.

If you have muriatic acid left over, you can either keep it for later or check out our blog article for how to dispose of leftover muriatic acid.

Why Add Muriatic Acid to a Pool?

Muriatic acid is used to lower alkalinity in pools. By lowering alkalinity you will also lower pH. High pH can damage your filtration system and make your pool chlorine ineffective.

High pH can cause the filter to work harder, the pump to work harder and your heater to work harder, which can all cause long-term damage.

pool-ph-diagram-showing-different-levels
Add muriatic acid to your pool to bring down the pH level to 7.4-7.6 – but don’t add the acid all at once.

A lower pH number in your pool means that it is more acidic.  A higher pH in pool water means the pool water is more alkaline or basic. Chlorine is less effective at sanitizing the water above a pH of 7.4 – increasing bacteria growth, which can lead to skin and eye irritation.

When a pool’s pH goes off-kilter, it can wreak havoc on the other chemical reactions taking place and might cause problems like cloudy water, scaling or corrosion.

How Much Muriatic Acid is Needed?

Review the product label to determine how much acid to add based on the current alkalinity and the volume of your pool (see table below).

Amount of Muriatic Acid to Reduce pH (and alkalinity)

Pool Volume (gal)< 7.2 pH7.2-7.6 pH8 pH8.2 pH8.4 pH8.6 pH
1,000Add Baking SodaIdeal3-5 fl oz4-6 fl oz5-8 fl oz6-9 fl oz
5,000Add Baking SodaIdeal15-25 fl oz20-32 fl oz23-37 fl oz27-44 fl oz
10,000Add Baking SodaIdeal32-48 fl oz55-87 fl oz47-74 fl oz55-87 fl oz
20,000Add Baking SodaIdeal2-3 quarts2½-4 quarts3-4½ quarts3½-5½ quarts
30,000Add Baking SodaIdeal3-4½ quarts3½-6 quarts4½-7 quarts5-8 quarts
Chart shows the amount of muriatic acid (hydrochloric acid) required to lower pH. Source data: https://app.poolcalculator.com

Can I Add Chlorine and Muriatic Acid at the Same Time?

You should never add chlorine and muriatic acid at the same time. The muriatic acid will react with the chlorine in your pool and create a deadly gas called hydrochloric acid. You need to wait for a minimum of 30 minutes, after you add the acid, before adding any chlorine to your pool.

In fact, it’s a good rule of thumb not to mix any pool chemicals together.

Pool chlorine and other chemicals.

When is it Safe to Swim after Adding Muriatic Acid?

It is safe to swim in your pool 30 minutes after adding muriatic acid. You’re waiting for the pool pump to circulate and distribute the acid evenly throughout the pool. Waiting means you won’t jump into an area of the pool with a strong concentration of acid.

To speed things up, you can stir the pool water to distribute the acid.  

Final Thoughts 

In conclusion, you should not add too much muriatic acid, or pour it in all at once. It is better to dilute it first in a bucket of water before adding it slowly into their pool. To do this you need to work out how much acid you need, based on the current alkalinity and volume of your pool.

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