Everything You Need To Know About Sodium Bisulfate In Your Pool


If you’re reading this post, you were probably doing a little research on how to lower the pH balance and total alkalinity in your pool with sodium bisulfate.

So let’s take a deep dive into sodium bisulfate and why you might use it in your swimming pool.

Sodium bisulfate, or dry acid, is an acid salt known as sodium hydrogen sulfate.

It can be used in a lot of ways such as food additives and cleaning, but in swimming pools, it’s often used to lower pH balance and total alkalinity when they get too high.

It’s usually processed into a white, grainy substance that can be stored in a container and used as needed.

Sodium bisulfate vs muriatic acid


Sodium bisulfate is not the only chemical that can be used to lower pH balance, of course—muriatic acid is also readily available for this purpose and it works just as well.

The problem with muriatic acid, though, is that it is a much more caustic substance that can burn the skin or damage your pool surfaces if you’re not careful.

But some people use muriatic acid in cleaning their tiles and removing buildup anyway, so they prefer to also use it to lower pH when needed.

It’s entirely your choice, but in my opinion, stick with sodium bisulfate whenever possible.

Importance of pH balance & alkalinity

Keeping your pool’s pH and alkalinity levels in check are important for water safety.

>>Read: How to lower alkalinity in your pool

For one thing, if either of those levels are off, your chlorine won’t be able to do its job very well.

Also, out of balance alkalinity and pH levels can cause corrosion or buildup on pool equipment, cloudy pool water, irritation to the eyes and skin, and a faster breakdown of chlorine molecules. 

So, yeah: they’re pretty important!

How to lower pH with sodium bisulfate

Step 1. Test your pool chemistry levels

First, you’ll need to test all your pool’s chemistry levels with either a liquid or strip pool testing kit. If the pH level is too high, you’ll need to adjust it with sodium bisulfate.

>>Read: How to choose the best pool test kit

Ideally, you should keep your pool’s pH levels between 7.2 and 7.6.

Most pH reducer products are made with a high concentration of sodium bisulfate, usually at least 93.2%.

And each product has its own instructions for use, so it’s important to read those before you attempt to use it.

Step 2. Determine the amount of sodium bisulfate

Once you’ve determined that your pH does in fact need to be reduced, you’ll need to figure out how much sodium bisulfate you need to add.

Most experts recommend adding about ¾ of what the instructions call for to begin with since you can always add more later.

Step 3. Determine whether to dilute

Then, read the instructions to find out whether or not your product needs to be diluted.

If it does, a five-gallon bucket is usually the best container to mix your acid and water in. 

Step 4. Add the sodium bisulfate

Now, add the sodium bisulfate to the pool.

For an inground pool, this is close to the return jets; for an above ground pool, this is along the pool wall.

This should distribute the product all throughout the pool within 15 minutes or so, and you’ll be able to tell when the product dissolves as it will disappear from sight.

Step 5. Let the product do its work

Next, allow the product to work for at least 6 hours.

Do not return to the pool until you have balanced the water! 

Step 6. Retest the water

After 6 hours, retest and add more dry acid if necessary.

You should test both pH and alkalinity because the two levels usually go hand in hand. 

How to lower alkalinity with sodium bisulfate

As a general rule, alkalinity should be between 80 and 120 ppm.

Alkalinity is what sort of stabilizes the pH levels, and usually if the pH is too high, alkalinity will be too low—so be sure to always test these two levels together.

If alkalinity is too low, it will cause etching, staining and burning eyes and skin. The pH levels will also be very unstable in this situation, sometimes bouncing up and down, which causes the sanitizer to lose its effectiveness.

Sodium bisulfate reduces both pH levels and alkalinity.

This can be a fairly slow process so you may have to be patient and keep adding product over the course of a few days to see the necessary changes.

Again, to use the product effectively, be sure to read the instructions, but here’s a good five-step overview:

Step 1. Find out how much product to use for your particular pool size and mix the dry acid with water if needed.

Step 2. Turn the jets off and wait about an hour before adding about ¾ of what the instructions call for the deep end of the pool.

Step 3. Pour the product slowly in a small stream—this keeps it from disrupting the pH balance as much as if you were to dump it all in or circulate it through the jets.

Step 4. Wait at least 6 hours and retest both alkalinity and pH levels.

Step 5. If you need to adjust either one, repeat the necessary steps every 6 hours until your pool is in balance.

Helpful tips for using sodium bisulfate

Although sodium bisulfate is much safer to use and store than muriatic acid, it’s still a toxic substance that should be used with caution.

  • Don’t swim in a pool after adding sodium bisulfate for at least 4-6 hours. It can cause serious burns to the skin if it comes in direct contact.
  • Never add more than the recommended amount of sodium bisulfate to your pool at one time. It can cause surface and plumbing damage.
  • Always add sodium bisulfate to the water slowly. Do not add water to sodium bisulfate.

Bottom line

As long as you’re keeping your pool maintained pretty regularly, you shouldn’t have too many problems with pH and alkalinity.

But when you do, they can both be a little tricky to balance.

This is mainly because pH is such an unstable factor, stabilized only by…you guessed it…proper alkalinity balance.

Because of this, they also both require a little more patience to balance than the others.

The main thing to remember is to set aside the time to test and adjust every few hours and make sure all the other levels are getting tested periodically as well. 

A balanced pool is a happy pool!

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