What Is Dry Acid and How Do You Use It In Your Pool?

Written by Michael Dean
February 7, 2024

dry acid for a swimming pool

If you are a pool owner, you’re likely already familiar with the amount of care and maintenance a pool needs. When it comes to pool maintenance, one chemical you may have heard of but may not entirely be familiar with is dry acid.

Understanding how dry acid works can help keep your pool water safe, clear, and inviting for all those who want to take a refreshing dip. So, let’s get into it! In this article, I will explore what dry acid is for pools, when to use it, how to use it, and more. 

Main Takeaways

  • Dry acid, or sodium bisulfate, is used in pools to balance pH and alkalinity.
  • Maintaining a slightly alkaline pH (7.2-7.6) prevents irritation and optimizes chlorine effectiveness.
  • Add dry acid for regular maintenance after adding chemicals and to manage alkalinity levels.
  • Another option for lowering pH in a pool is muriatic acid, which is cheaper but more dangerous to handle.

What Is Dry Acid For Pools?

Dry acid is a fine, granular substance used to adjust and control the pH levels of pool water. Dry acid is known by many other names, including sodium bisulfate, acid salt, sodium hydrogen sulfate, sodium acid sulfate, and more.

Just look at the ingredients list on this dry acid at Leslie’s pool supply store – it’s sodium bisulfate!

Like the more popular muriatic acid, dry acid is used to lower the pH of pool water when it becomes too alkaline (above 7.6). By adding dry acid to a pool with a high pH, you will lower your pH level and maintain it within the recommended range of 7.2 to 7.6. This helps ensure a safe, comfortable, and visually pleasing swimming environment while also prolonging the life of your pool and equipment.

As a plus, since dry acid is, as you can guess from its name, dry, it is generally safer and easier to handle compared to liquid acids like muriatic acid.

When to Use Dry Acid In Your Pool

The water in your pool has a pH level that indicates whether it’s acidic or alkaline. And if you find that your pool is too alkaline (above a pH of 7.6), you can add dry acid to the pool water to lower the pH and total alkalinity.

pH hovers on a scale from 0 to 14, where 7 is neutral. A pH below 7 is considered acidic, while a pH above 7 is alkaline. Pool water ideally should maintain a slightly alkaline pH level between 7.2 and 7.6. A pool water pH level above this range can lead to various issues for swimmers, such as skin and eye irritation, cloudy water, and reduced effectiveness of chlorine. 

You should always start by testing your pool’s current pH level. You can purchase a reliable pool testing kit from your local pool supply store or online to determine the pH level of your pool water. Now, if your pH is too high, this is where an acid like dry acid comes into play.

Below are the primary use cases for using dry acid in your swimming pool.

For Regular Maintenance

You can add dry acid to your pool as part of your regular pool maintenance routine. As a pool owner, you must regularly test your pool’s pH. This is especially the case after you add new water, after a pool party, or after heavy rainfall. All of these can mess with a pool’s pH, so always test the water and adjust as necessary. If the water is too alkaline, it’s time to add dry acid!

After Adding Chlorine and Other Chemicals

It’s absolutely imperative that you test the water’s pH level after you add chlorine or other pool chemicals as well. When added to pool water, certain chlorine types and chemicals can cause the pH to rise. Test the pH if you’ve recently shocked your pool or added a significant amount of chemicals. Then, add the required amount of dry acid to return it to the desired range of between 7.2 and 7.6.

To Manage Alkalinity Levels

Dry acid helps you lower both pH and alkalinity in your pool effectively. You can test the total alkalinity level of your pool by using a water testing kit. The ideal range for alkalinity is between 80 and 120 parts per million (ppm). If your test indicates a higher alkalinity level, use dry acid to lower it.

How to Add Dry Acid to Your Pool

Adding dry acid to your pool is a straightforward process. Here’s my handy step-by-step guide to help you along the way.

Step One: Test the pH Levels

First things first, begin by checking your pool’s pH level with a pool testing kit. The ideal pH range is between 7.2 and 7.6. If your pH is higher than 7.6, it’s time to get out that dry acid!

Step Two: Determine How Much Dry Acid to Add

Use my handy pH calculator to determine how much dry acid to add to your pool. If you’d prefer to do the calculations manually, follow the manufacturer’s instructions. Note that the amount of dry acid you add will depend on the current pH of your pool and the pool size.

Remember, it’s best to start with ¾ of the recommended amount to avoid overdoing it. Here’s a pretty standard dry acid from Leslie’s.

Leslie's Dry Acid

You can get Leslie's Dry Acid (sodium bisulfate) online if you don't have a Leslie's Pool Supplies store near you.

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Step Three: Add the Dry Acid

There are two ways to add dry acid. Always refer to the manufacturer’s instructions to know which method to use:

  1. Pour the dry acid near the pool’s return jets, and avoid adding it near the skimmer! 
  2. Pre-dissolve the dry acid in a 5-gallon bucket of water. Make sure you add to the dry powder to the water and not the other way around! 

Dry acid doesn’t work instantly. Give it time, at least 6 hours, for it to do its job. Stay out of the water during this time and let the dry acid work its magic!

Step Four: Retest the pH

After the waiting period, test your pool’s pH again. If needed, you can add more dry acid.

But what happens if your pH is lower than 7.2? In that case, you’ll need to raise the pH with the help of soda ash or sodium bicarbonate, AKA baking soda.

What Does Dry Acid Do to Alkalinity?

First of all, what is alkalinity? Alkalinity helps keep the pH level from fluctuating too much, providing swimmers with a stable and comfortable environment. It’s an essential parameter to consider alongside pH; the two are closely intertwined.

When you add dry acid to your pool, it not only reduces the pH level but also has the effect of decreasing alkalinity. This is especially beneficial when your pool’s alkalinity levels are above the ideal parameters of between 80 and 120 ppm.

How Long to Wait to Swim After Adding Dry Acid

After adding dry acid to your pool to adjust the pH level, you have to be patient before taking that refreshing plunge. Typically, I recommend waiting at least 6 hours before allowing swimmers back into the pool. During this period, the dry acid has the chance to thoroughly mix with the water, ensuring that the pH level stabilizes within the recommended range of 7.2 to 7.6. 

However, remember that this waiting time can vary based on factors such as the dosage amount, pool size, and the efficiency of your filtration system. So, always make sure to use a reliable pool water testing kit to confirm that the pH level is within the desired range before you jump back into the pool. While the water may look inviting, safety always comes first!

Dry Acid vs. Muriatic Acid

When it comes to adjusting pH levels in your swimming pool, two of your options are dry acid and muriatic acid. Although both acids serve the same essential purpose – maintaining proper pH – they are different. So, which one should you opt for?

Dry acid is user-friendly and safer to use. Plus, you can generally add dry acid directly to the pool water without diluting it. However, dry acid is generally a more expensive option.

Muriatic acid is often the preferred choice between these two acids. The reason for this often boils down to money. Muriatic acid is cheaper than dry acid! However, on the flip side, handling muriatic acid requires absolute caution due to its corrosive properties.

Ultimately, your choice between dry acid and muriatic acid will depend on your pool, budget, and your familiarity with chemical handling.

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Frequently Asked Questions

Can you add dry acid and chlorine at the same time?

You should never mix different chemicals together! In fact, you should never mix any type of acid (including dry acid) with any type of chlorine, as the resulting fumes of this combination can be toxic and dangerous.

What is better: dry acid or muriatic acid?

There’s no real right or wrong answer to this. If you want an acid that is easier to handle and don’t mind paying extra for the convenience, go for dry acid. However, if you want a stronger chemical for a cheaper price, opt for muriatic acid.

An Alternative To Muriatic Acid

Dry acid is not the most common chemical used in swimming pools, but it certainly can be used. In fact, if you have some dry acid on hand or pool stores are out of stock of muriatic acid, dry acid is a terrific alternative.

Do you have more questions about using dry acid in your pool? Reach out to me. I’ll happily answer any questions you have!

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