When it comes to lowering pH and alkalinity in a pool, the best options you have at hand are dry acid and muriatic acid. Both are powerful and useful substances with disadvantages and advantages, so you might be wondering which one you should use.
In this article, I will compare dry acid and muriatic acid, go over how to use them, and answer the ultimate question: which one is the best to use in your swimming pool?
Main Takeaways
- Dry acid and muriatic acid are both used in pool maintenance to lower pH levels.
- Muriatic acid and dry acid differ in chemical composition, physical form, ease of handling, price, safety, and compatibility.
- Generally, I would recommend using muriatic acid over dry acid, as it is versatile, more affordable, and doesn’t contain sulfates.
What Is Dry Acid?
A substance that can be used to lower pH and oxidize contaminants in the water, dry acid is also simply known as sodium bisulfate. Dry acid is much less common than muriatic acid, but it is a safer alternative. Almost always found in granular form, you can easily dissolve this acid in a small batch of water before being added to the pool. It is white and powdery in appearance, which makes it easier to store and handle.
However, just because it is easier to handle doesn’t mean you shouldn’t handle it with care. As with any other corrosive and harmful substance, make sure you are following proper safety protocols when you work with dry acid.
What Is Muriatic Acid?
Muriatic acid is a diluted form of hydrochloric acid. This is a powerful, corrosive substance that is used in a range of industrial, commercial, and household activities, ranging from cleaning, rust removal, scale removal, pH adjustment, and water treatment. Most pool owners use muriatic acid to lower pH levels in the water, as it is the most accessible and affordable method. Beyond pH adjustment, you can use muriatic acid for other purposes, including acid washing.
This pool chemical is colorless and has a pungent odor. What makes muriatic acid such an effective tool for lowering pH is its highly acidic nature. It has an extremely low pH of 1! So, you’ll need to take care when handling this chemical since it is such a potent acid. Muriatic acid can cause severe chemical burns if it comes into contact with the skin, eyes, or nasal passages, so proper safety practices are important. I strongly recommend researching and learning how to handle muriatic acid before using it in case you’re unfamiliar with how to do so.
Dry Acid vs. Muriatic Acid: The Differences
Dry acid and muriatic acid are both used in pool maintenance to lower pH levels. However, they have distinct differences in their properties, uses, prices, safety precautions, and more. So, what is the difference between these two chemicals?
Chemical Composition
Dry acid is sodium bisulfate (NaHSO4), whereas muriatic acid is hydrochloric acid (HCl).
Physical Form
As you might be able to guess from its name, dry acid is typically sold in granular or powdered form. On the other hand, muriatic acid is sold as a liquid.
Ease of Handling
Dry acid is safer and easier to handle than muriatic acid because it is not a liquid. Muriatic acid requires more careful handling due to its liquid form, strong fumes, and corrosive nature.
Price
Dry acid is often more expensive per pound than muriatic acid. This price difference is one of the main reasons why most pool owners prefer muriatic acid.
Safety
Dry acid is most definitely a safer and easier to use substance than muriatic acid. But, while safer than muriatic acid, dry acid should still be handled with care. It can still cause eye and skin irritation if handled carelessly. On the other hand, muriatic acid demands strict safety precautions, including wearing appropriate protective gear, working in well-ventilated areas, and careful storage.
| Dry Acid | Muriatic Acid | |
| Chemical Composition | Sodium bisulfate (NaHSO4) | Hydrochloric acid (HCl) |
| Physical Form | Granular | Liquid |
| Ease of Handling | Easier to handle | More difficult to handle |
| Price | More expensive | Less expensive |
| Safety | Safer | More dangerous |
Is Dry Acid or Muriatic Acid Better for Pools?
The choice between dry acid and muriatic acid for pool maintenance depends on several factors—there is no one-size-fits-all answer! But here are the four main points to consider before you make your decision.
Handling
The winner: dry acid
As mentioned above, dry acid is granular instead of a liquid, so it is much easier to handle than muriatic acid. Therefore, when handling dry acid, there is less chance of accidental spillage or splashing onto your clothes or skin! You are also less likely to inhale any dangerous, toxic fumes, as would be the case with muriatic acid. However, the one caveat is that you would need to be careful when using it on windy days! On the other hand, muriatic acid requires stringent safety precautions to avoid damaging your pool, surroundings, and yourself.
Cost
The winner: muriatic acid
Muriatic acid easily wins this round, as it is cheaper than dry acid. That said, it’s not generally a significant difference, especially if you buy in bulk.
Sulfates
The winner: muriatic acid
As you know, dry acid is also known as sodium bisulfate. This means it contains sulfates. If you have a sulfate level higher than 300 parts per million (ppm), your pool surfaces may degrade, and your pool equipment may corrode. So, if you use dry acid, you’ll need to constantly monitor your sulfate levels, especially since they’re quite difficult to get rid of. On the other hand, muriatic acid doesn’t contain any sulfates.
How to Lower pH with Dry Acid
Lowering the pH of your pool water using dry acid is a straightforward process. Here’s how:
- First, test your pH levels—the ideal range for pool water is between 7.2 and 7.6. If it’s higher than this, you need to lower it.
- Calculate the dosage of dry acid needed to be added to the pool to lower it to the right pH levels. Use my pH calculator to help calculate how much you’ll need.
- Then, pre-dissolve the dry acid in a clean 5-gallon bucket filled with pool water. This helps mix the product properly and avoid any concentrated areas of the acid.
- Once the solution is mixed, walk around the perimeter of your pool and slowly pour the solution into the water.
- Run your pool pump and filter for the next few hours to allow for the solution to mix evenly.
- Retest the water. The pH should be balanced after around 6 hours. If it’s not, add more dry acid to the water.
- Monitor the pH level regularly and make adjustments as needed.
How to Lower pH with Muriatic Acid
Muriatic acid is very strong. So, before you handle it, you need to don some protective gear. Safety-grade chemical-resistant gloves, boots, goggles, and a mask are a must when handling muriatic acid in case of splashes or fumes. Here’s my guide on how to use it:
- First, determine your pH levels by testing your pool water and figure out if your pH is too high. If above 7.6, you need to lower it.
- To check how much muriatic acid to add to your pool, you’ll need to calculate the dosage based on the volume of your pool and the current pH level. Follow the manufacturer’s instructions to calculate how much you’ll need. But you can also use my pH calculator if you’d rather not do the math.
- It’s vital to pre-mix muriatic acid before adding it to the pool. In a clean plastic container full of clear pool water, add the calculated amount of muriatic acid. Never add water to the acid—always add acid to the water!
- Pour the solution into the water and run your pool pump and filter for the next few hours to allow for it to mix evenly.
- Retest the water, and make sure the pH is between 7.2 and 7.6. If it’s not, repeat the above steps to add more muriatic acid. Opt for gradual adjustments, not drastic shifts.
- Monitor the pH level regularly and make adjustments as needed to keep it within the healthy pH ranges.
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Frequently Asked Questions
Is dry acid the same as pH Down?
Yes, dry acid is often referred to as “pH Down” or “pH minus.” However, these products will generally cost more than plain old muriatic acid, as it is specifically marketed to lower pH levels.
Is dry acid safe?
Yes and no. Dry acid is a lot safer to handle than most pool chemicals, including muriatic acid, but it should still be handled with proper care, following the right safety precautions.
Can you swim after adding muriatic acid to the pool?
Not immediately. After adding muriatic acid to a pool, please wait until the acid has been fully dispersed and the pH level has returned to safe ranges before swimming. This means being patient for 2 to 3 hours at the very least!
Muriatic vs. Dry Acid: The Verdict
In my opinion, despite it being a potent (and potentially hazardous) substance, muriatic acid is more useful a product to have at hand as a pool chemical, owing to its economic value, versatility, and general effectiveness at lowering pH. Dry acid may be easier to handle, but it is generally more expensive and contains sulfates, which can be harmful to your swimming pool over time. However, this doesn’t mean you shouldn’t use dry acid. Ultimately, what you use is entirely up to you and what you are comfortable with.
Do you have any more questions about pool chemicals? Let me know; I’m happy to help. In the meantime, you can read more of my pool chemicals research in my main article on swimming pool chemistry basics.
