Home » Soda Ash vs. Baking Soda for Hot Tub: Which is Better?

Soda Ash vs. Baking Soda for Hot Tub: Which is Better?

If you are a hot tub owner, you will want to do everything to keep it in the best shape possible. Maintaining a healthy hot tub, sometimes called a spa or Jacuzzi, involves making sure that the chemical levels are balanced. This is where the baking soda and soda ash come in.

They are both helpful in maintaining healthy PH levels and total alkalinity. But which is better?

Soda ash (sodium carbonate) is best for raising a hot tub’s pH level in large amounts. It will also raise the alkalinity. Baking soda (sodium bicarbonate) should be used for raising the alkalinity of a hot tub or spa. Baking soda has a negligible effect on the pH.

There’s a little more to it than that though. Read on to learn about the pros and cons of each of these.

Soda Ash Vs. Baking Soda for Your Hot Tub

Both soda ash and Baking soda raise the alkalinity and pH in a hot tub. But they are used for different purposes. Therefore, you must understand how each works before you can decide which one to use.

Even though some may view this as a minor issue, it is a critical aspect of proper hot tub maintenance.

Maintaining a proper pH level is crucial if you want to have properly treated water for your hot tub.

Incorrect pH in a hot tub can cause:

  • Corrosion of the hot tub and its equipment
  • Ineffective sanitization
  • Increased chlorine demand
  • Swimmer discomforts like irritation of the skin and eyes – which can be very unpleasant

With that said, the following information is intended to help you better understand how soda ash and baking soda can help you balance your hot tub’s pH levels.

What is Soda Ash (Na2CO3)?

Soda ash, which is also called sodium carbonate, is a white, odourless, water-soluble salt that produces temperately alkaline solutions in water. It is made from salt and limestone through an ammonia-soda process.

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It has a pH of around 11.5.

Soda ash, (sodium carbonate) is regarded as the 10th most consumed inorganic compound globally. It is a safe, simple compound used for various industrial processes and an essential chemical for the treatment of hot tubs and swimming pools.

What is Baking Soda (Sodium Bicarbonate)?

Baking soda is a white crystalline powder. It can also be called sodium bicarbonate (NaHCO3). It consists of one atom of sodium, one atom of hydrogen, one atom of carbon, and three oxygen atoms.  

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It is also known as bicarb soda and has a pH of around 8.3.

Again, it’s used in both hot tubs and swimming pools and increases the alkalinity of the water. It’s generally labelled with names such as “Alkalinity Up, “Alkalinity Increaser”.

Differences Between Soda Ash and Baking Soda                    

The biggest difference when using either of these chemicals for your hot tub is the effect they have on the pH. Soda ash significantly raises the pH whereas baking soda will only raise it a small amount. They will both increase the alkalinity but baking soda will increase this more.

Soda Ash            

  • Soda ash raises pH and raises alkalinity
  • Soda ash has a pH between 11.3 – 11.7
  • Primarily used to raise pH in large steps
  • Soda ash can easily cloudy the water

Baking Soda

  • Baking soda will significantly raise alkalinity and only slightly increase the pH
  • Baking Soda has a pH of 8.3
  • Primarily used to raise the alkalinity

Cost of Baking Soda vs Soda Ash

Although baking soda is less expensive per pound, you’ll need 4-10 times the amount of baking soda to raise the pH compared to soda ash. That’s quite a lot more.

Soda Ash

Soda ash costs about $30 for 10 pounds.

7 oz of soda ash per 10,000 gallons (37,854 L) will raise pH by roughly 0.1.  This amount does vary a lot depending on the chemistry of the water. Start small using half of what you think you need. You can always add more. It’s harder to fix your mistakes.

Baking Soda

Baking soda costs almost half of that, at about $16 for 10 pounds.

A rough rule for how much to use is that 1.5 lbs of baking soda per 10,000 gallons (37,854 L) of pool water will raise alkalinity from 10 ppm. Baking soda will raise the pH a little bit too.

This amount is approximate only as the exact amount depends on many other factors.

Similarities Between Soda Ash and Baking Soda

  • Both chemicals raise pH levels and alkalinity but they don’t raise these levels in equal amounts.
  • Both chemicals have side effects if the wrong quantity is applied in your hot tub. Soda ash is quite likely to lead to your water being cloudy. Too much baking soda can scale in your hot tub.

What is Better About Soda Ash?

At some time during your time as a hot tub owner, you’ll find that the pH is way too low. This is where soda ash comes in. If you’re looking to raise the pH in your hot tub quickly and by a large amount, pick soda ash over the baking soda.

Whilst baking soda can raise the pH in your hot tub, it takes a substantial quantity of baking soda to increase pH in a hot tub. So much that you will likely increase the alkalinity too much.

The best level of alkalinity in your hot tub should be between 80 and 120 parts per million (ppm).

Stick to soda ash if your alkalinity is about right and your main goal is to raise the pH levels in your tub.

What is Better About Baking Soda?

Baking soda is better than soda ash for raising total alkalinity in a hot tub. It’s used primarily if you don’t want to increase the pH level. Although it will slightly increase pH – but that’s an easy fix. Just add a little muriatic acid or sodium bisulfate to decrease the pH.

Baking soda is also easy to find and cheap to buy.

Apart from being used in your hot tub, baking soda (sodium bicarbonate) can also be used for other purposes in the home. For instance, you can use it for cleaning and baking.

Yes, it’s the same stuff. Only it costs less than the stuff you’ll find in the hot tub and pool supply stores.


Hot tubs require a pH balance in the midrange of 7.4-7.6, which will let the chlorine work efficiently. It’s also essential to the comfort of the swimmers and the health of the hot tub equipment.

Soda ash is a good choice for your hot tub if you generally wish to raise the pH level in large amounts. Whereas, baking soda is best if you want to raise the alkalinity without raising the pH of your spa.

However, the bottom line is that if you are experiencing low pH and total alkalinity levels, you’ll need both soda ash and baking soda on hand.

Related Reading:
How Long Does It Take to Heat a Hot Tub? (and Tips for Faster Heating)
How to Shock a Hot Tub
2 Ways to Raise pH in Hot Tub (pH is Low)
Do You Need to Shock Hot Tubs?
How to Lower Hot Tub pH Naturally (Using Vinegar)
Can You Fill a Hot Tub or Spa with Well Water?
Chlorine Vs Bromine for Hot Tubs (Which is Better?)

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