Can I Use Baking Soda to Raise the pH in My Hot Tub?

We hear this question quite often: “Can I just use baking soda to raise the pH in my hot tub?”

Baking soda is inexpensive, easy to find, and you may have heard that it can be used instead of traditional pH Up. While baking soda can affect your water chemistry, it does very little to help increase the pH in your hot tub.

Baking soda is sodium bicarbonate, which is primarily used to raise total alkalinity. Most pH Up products use sodium carbonate, which is much more effective at raising pH.

So before reaching into the kitchen cabinet or buying bags of baking soda for your hot tub, let's explain the difference and why it matters.

Sodium Carbonate vs. Sodium Bicarbonate

Part of the confusion comes from the names. Sodium carbonate and sodium bicarbonate sound almost identical, but they are two different chemicals and affect your hot tub water differently.

You may also see baking soda labeled as sodium hydrogen carbonate. Don't let the different name confuse you. Sodium hydrogen carbonate and sodium bicarbonate are two names for the same chemical.

Sodium Bicarbonate (Sodium Hydrogen Carbonate) = Baking Soda

Baking soda is primarily used to increase total alkalinity. It can have some effect on pH, but it is not nearly as effective at raising pH as sodium carbonate.

Sodium Carbonate = Soda Ash / Commonly Used as pH Up

Sodium carbonate is a different chemical. It has a much stronger effect on pH, which is why it is commonly used in products designed specifically to raise the pH of hot tub water.

So while sodium carbonate and sodium bicarbonate may sound almost the same, they should not be treated as interchangeable products when adjusting your hot tub water.

Where Did the Idea of Using Baking Soda to Raise pH Come From?

There is actually some truth behind it.

Baking soda has been used in swimming pool and spa water care for many years, and adding it can cause the pH to increase somewhat. This has led to a lot of advice online saying that if your pH is low, you can simply add baking soda.

The problem is that baking soda is primarily used to increase total alkalinity, not pH. Because pH and total alkalinity are closely related, increasing the alkalinity can sometimes cause the pH to rise as well. This can make it appear that baking soda is doing the same job as pH Up.

It isn't.

Another reason for the confusion is simply the names. Sodium bicarbonate and sodium carbonate sound very similar, making it easy to assume they're basically the same product.

Both have a place in hot tub water care, but they serve different purposes.

What Happens If You Keep Adding Baking Soda?

This is where using baking soda as a substitute for pH Up can create another problem.

If your pH is low and you continue adding baking soda trying to bring it up, you are also continuing to increase the total alkalinity of the water.

You may eventually end up with alkalinity that is much higher than it should be while still not getting the pH adjustment you were looking for.

Instead of continuing to add more baking soda, test both your pH and total alkalinity and adjust whichever one actually needs correction.

So What Should You Use?

• If you need to increase the total alkalinity in your hot tub, sodium bicarbonate (baking soda) can be used.

• If you need to increase the pH, use a pH Up product made specifically for above-ground hot tubs that contains sodium carbonate.

Can you buy sodium carbonate somewhere other than a hot tub or spa store? Sure. However, household products aren't necessarily made or labeled for use in hot tub water and may contain additional ingredients you don't want to add to your spa.

That's why we recommend using water-care chemicals made specifically for above-ground hot tubs. You know what you're putting into the water, the product is intended for spa use, and you'll have proper dosing instructions for the much smaller volume of water found in a hot tub.

The Bottom Line

Baking soda isn't the same thing as pH Up.

Sodium bicarbonate (baking soda) is primarily used to increase total alkalinity, while sodium carbonate is much more effective when you need to increase the pH.

Both chemicals have a purpose in hot tub water care. The important thing is knowing what your water actually needs before adding either one.

Test your water first, determine whether your pH or total alkalinity is low, and then use the appropriate product to correct it.

Baking soda for low alkalinity. pH Up for low pH.