Perhaps you’ve recently tested the pH and alkalinity of your pool and realized they were too high so now you’re trying to lower them using muriatic acid. In this article, I’ll help you determine the exact amount of muriatic acid you’ll need to lower these water chemicals, as well as the step-by-step procedure.
To lower the pH using muriatic acid, 12 ounces to 1 quart should be used per 10,000 gallons (45,461 L) of pool water. The amount of muriatic acid needed to lower your pool pH and alkalinity will depend on the initial levels of these chemicals, how strong the muriatic acid is, and the volume of your pool.
The higher the chemical levels are and the more volume your pool has, the more you’ll need. The stronger the acid is, the less you’ll need.
Before we dive into the topic, let’s first take a look at what muriatic acid is exactly so that you’ll know why it works the way it does.
What is Muriatic Acid?
Muriatic acid is a type of pH down/pH reducer used to lower pool water’s pH and alkalinity. You can think of it as a watered-down version of hydrochloric acid. It comes in a liquid form and in several concentrations, so the amount you need will be proportional to the size of your pool and inversely proportional to the strength of the product.
As an acid, muriatic acid can be dangerous to handle, however it can quickly lower the pH and alkalinity of your pool water and allow you to get back to enjoying the pool in a matter of minutes. More details on how muriatic acid works can be found here: Muriatic Acid for Pool
Factors that Affect Amount of Muriatic Acid
The three factors that affect the amount of muriatic acid you’ll need to add are the:
- Initial levels of the pH and alkalinity
- Strength of the muriatic acid
- Volume of pool
1. Initial pH and Alkalinity Levels Determine How Much Muriatic Acid to Use
Before adding muriatic acid to your pool water, you’ll have to test your water to see where your pH and alkalinity levels are initially. Depending on how much they’ve strayed from their optimal ranges, you’ll be able to determine how much muriatic acid you’ll have to add to lower them back to normal.
The more the difference is between their initial levels and their optimal levels, the more you’ll muriatic acid you’ll have to add.
2. How Strong Your Muriatic Acid is Will Determine How Much of It You’ll Need
Muriatic acid comes in several concentrations ranging from 15.7% to 31.45%. Many pool stores sell 28 – 31% acid. This is fine.
But if you’ve ever come across a lower concentration product, you’ll find that you need more of it to achieve the same effect as that of a higher concentrated one.
We’d recommend you choose a lower concentrated product due to the corrosive nature of muriatic acid, though it might take you additional doses to bring your water pH and alkalinity levels back down to normal.
Related Reading: What To Do If You Add Too Much Muriatic Acid To Pool
3. The Greater the Volume of Your Pool, the More Muriatic Acid You’ll Need
The amount of muriatic acid you’ll need is directly proportional to the volume of your pool. If you had two pools of different volumes with the same water chemical levels, you’ll need more muriatic acid for the larger pool than the smaller pool since there’s more water to cover.
Calculating Muriatic Acid Amount for Pool
The general idea when it comes to calculating the amount of muriatic acid needed for your pool is to first test the water chemistry and then follow the instructions on your product to determine how much muriatic acid you’ll need to lower the levels back down to normal for your pool size.
Of course, the exact amount will depend on many factors.
A general rule for 10,000 gals (45,461 L) of pool water, here’s how much muriatic acid you will need:
|Amount of Muriatic Acid (31.45%)
|8.4 or higher
To explain, you should add 12 ounces, 16 ounces, 24 ounces, and 1 quart of 31.45% concentrated muriatic acid per 10,000 gallons (45,461 L) of pool water if your starting pH level is between 7.6-7.8, 7.8-8.0, 8.0-8.4, or is above 8.4 respectively.
And if you have a 10,000-gallon (45,461 L) pool, it’s safe to assume that 20 ounces of acid will be enough to lower the alkalinity by 10 ppm.
As long as you bring your pH level down to just below the optimum range, the alkalinity should also drop to normal.
Typically, you’ll be able to find the exact amount that you need based on the instructions on the product’s label. However, if for any reason it’s not enough for you to calculate the amount, you can use this calculator.
Important: Add muriatic acid a little at a time instead of adding too much, as it’ll be easier for you to add more later than to remove the excess acid.
How Much Muriatic Acid to Lower pH
Assuming that you’re using 31.45% concentrated muriatic acid and have a 10,000-gallon (45,461 L) pool, here’s a visualization of the different amounts of acid you’ll need depending on your initial pH level.
How Much Muriatic Acid to Lower Alkalinity
Alkalinity levels in your pool water should not go beyond 140 ppm. To lower alkalinity, you’ll need to lower the pH and alkalinity together using muriatic acid, then aerate the pool to raise the pH back up to its optimal level of 7.6. Aerating is essential as the pH must drop below 7.6 (preferably to 7.2) for the alkalinity to drop as well.
In this chart, we’ll take a look at how different initial alkalinity levels can affect the amount of 31.45% concentrated muriatic acid needed to lower it for a 10,000-gallon (45,461 L) pool. Since pH needs to be at 7.2, we’ll assume we’re starting with a 7.6 pH (the optimal level).
How to Safely Add Muriatic Acid
Here are the materials and steps needed to safely add muriatic acid to your pool. Remember that a muriatic acid is a form of hydrochloric acid, so it’s highly corrosive and should be handled with care.
- Safety goggles
- Acid-resistant gloves
- Chemical-resistant apron
- Plastic 5-gallon (23 L) bucket
- Wooden/plastic stirrer
- Pool-grade muriatic acid
Procedure to follow:
- Test your pool water using either test strips or a digital test kit to figure out the current pH and alkalinity levels;
- Calculate the amount of muriatic acid you’ll need by figuring out the pool volume size and muriatic acid strength. Typically, how much you’ll need will be shown on the product;
- Turn on your pump to circulate the water before adding the acid;
- Dilute the acid in water in a 1:10 ratio. Be sure to add the water first and then the acid to your acid-resistant bucket. Stir with the wooden/plastic stirrer. Add the solution to the deep end of the water;
- Let the acid circulate for at least 30 minutes;
- Retest the pool water to make sure chemical levels are back to normal. If it’s not enough, add another dose of the acid;
- Aerate your pool water if the pH has dropped too low by turning on the return jets and pump.
Related Reading: Can I Add Muriatic Acid All at Once? | How to Safely Add
Can You Pour Muriatic Acid Directly into Pool?
Muriatic acid can be safely poured directly into your pool, but you have to be extra cautious by wearing the appropriate safety gear. Be sure to pour the acid into the deepest end of the pool.
You should also walk away as you pour so that you don’t breathe in the fumes. Diluting the acid in water is not required, but will make the addition process easier and safer to handle.
Alternatives to Using Muriatic Acid
If, for any reason you find it hard to obtain muriatic acid, here are some alternative options to consider.
- Sulfuric Acid: an alternative acid that requires a similar dosage to muriatic acid, 26 ounces of 38.5% sulfuric acid will be enough to lower the alkalinity by 10 ppm and pH an equal amount in a 10,000-gallon (45,461 L) pool.
- Sodium Bisulfate: a popular, safer, though the more expensive alternative to muriatic acid. It requires approximately 34.4 ounces of 93.2% sodium bisulfate to achieve the same effect as a 31.45% concentration of muriatic acid in a 10,000-gallon (45,461 L) pool.
Can you Use Vinegar Instead of Muriatic Acid?
In theory, you can use vinegar instead of muriatic acid as a natural way of lowering the pH in your pool. However, for practical reasons, you probably shouldn’t.
While vinegar can bring down the pH of the water, it has some risks that you should be aware of. One is that, even though it’s acidic, vinegar isn’t nearly as pure as muriatic acid, therefore it’ll require an enormous amount of it to make the same impact as regular muriatic acid.
This, of course, will create quite a strong smell that’s not particularly welcome in a pool.
Second, vinegar adds a bunch of organics, such as acetates, to your water, which, even though they won’t do much harm, aren’t particularly welcome either since they can prove troublesome to remove.
It’s best to always minimize byproducts and extra chemicals in your pool.
Related Reading: How to Lower Hot Tub pH Naturally (Using Vinegar)
Even though it may seem like a daunting task, figuring out how much muriatic acid to add to your pool is essential to providing a safe and healthy experience in the water.
It’s also relatively easy since there are only three factors to consider and most of the time, the directions will be on the bottle. And remember, if you ever need additional help, there’s always the online calculator that you can use to easily get the amount you’ll need.