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Can I Put Baking Soda in My Hot Tub?

By: Author Jeff Campbell

Posted on  - Last updated:

Categories Hot Tub Operational Tips, Hot Tub Water Chemistry

The cost of chemicals is a large part of the price of owning a hot tub. So many owners look for cheaper alternatives, some asking, “can I put baking soda in my hot tub?”

Regular household baking soda can be used in a hot tub to raise both alkalinity and pH. However, due to its minimal impact on pH and the large amount needed to make big adjustments, it is best used to raise the total alkalinity.

In this article, we will look at what baking soda is and how it differs from “spa-up-type” products, why you would want to put it in your hot tub, and if it’s truly the most economical way to adjust alkalinity. And we’ll also get into exactly how much to use.

So, let’s waste no more time and dive in.

Ready to Spend Less Time On Maintenance and More Time Enjoying Your Hot Tub?

Let’s face it. Balancing the water, cleaning filters, dealing with rashes, and trying to figure out which chemicals to buy and add can make you feel more like a chemist than someone who just wants to relax after a long hard day!

That’s exactly why The Hot Tub Handbook and Video Course is so valuable!

This is from Matt over at Swim University and he developed it for people looking to save money, time, and frustration. His tips on chemicals can save you $100/year just by making sure you buy only what you need.

So if you’re ready to stop being confused or frustrated with your hot tub and start spending more time in it, check out The Hot Tub Handbook and Video Course.

Just click that link to learn more on their website.

baking soda in a hot tub lg

What does sodium bicarbonate do to spa water?

Sodium bicarbonate increases the hardness of spa water, and also raises the alkalinity while having a minor upward impact on pH. Sodium bicarbonate is the chemical name for baking soda.

So why are we concerned with water hardness?

Well, calcium scale build-up in the pipes and pump is a result of hard water, and this can damage your hot tub by causing the equipment to burn out. This happens as the calcium builds up and restricts the water flow.

If you’ve ever seen chalky build-up around your shower head, you have hard water.

It is also important to keep the pH level between 7.2 and 7.8 parts per million (ppm). If the pH is too high, it can lead to foam build-up on the surface and a musty or stale odor. High pH can also cause dry, itchy skin.

You should test the water frequently to make sure it is within range. Always test the alkalinity first and adjust that before playing around with the pH.

Total alkalinity should be between 80 and 120ppm.

If the pH is low – below 7.2ppm – don’t use baking soda. You would end up having to use a ton of it. Use pH-up or a spa-up product. Just be aware that any product for pH will affect alkalinity (and vice versa).

But baking soda is great for raising alkalinity, and it will only have a minor impact on pH. If you need to raise the alkalinity, start with 6 tablespoons of baking soda for a large hot tub and adjust as needed.

Can I use baking soda to raise the pH in my hot tub?

Yes, you can use baking soda to raise the pH value of the water in your hot tub, but it’s less than ideal due to the large amount needed to make a large impact. Baking soda is used mostly for raising the alkalinity of the water.

Many people get confused about pH and alkalinity, and I can understand the reason.

That’s why I wrote about it in a recent article. I explained how they differ and also how one relates to the other. I also explained what to do if you need to raise or lower one and not the other.

Just click that link to read it on my site.

A better product for raising pH would be sodium carbonate, better known as soda ash. This has a much higher pH value (over 50% higher) than baking soda, and because of this, it will raise both pH and total alkalinity.

Soda ash and baking soda are more effective when diluted in water first but always add the chemical to the water, not the other way around.

If you want to use baking soda to raise the pH, maybe it’s all you have at the time, it’s fine to do so, but you should read on to find out the pros and cons.

How much baking soda does it take to raise the pH in a hot tub?

Provided total alkalinity is in range, use 0.16oz (1/3 of a tablespoon) of baking soda for every 100 gallons of water to raise the pH by 0.1-0.2ppm. That means, to raise the level from 7 to 7.2ppm in a 500-gallon hot tub, it will require 0.8 ounces, which is just less than 2 tablespoons.

However, alkalinity is also affected by baking soda, so you may find that it is getting high as well.

The simple rule is 1 tablespoon of baking soda, which is about half an ounce, for every 100 gallons of water. The average large-sized hot tub is about 500 gallons or more.

But it’s not quite that simple in reality.

Baking soda has a pH of around 8.3ppm, which is not that much higher than the top end of the range for hot tub water, and this is why you need so much to raise the level by a significant amount.

You must be careful not to overdo it. High pH can be equally damaging as low pH.

If the pH level in a hot tub gets above 7.8ppm, you shouldn’t go in the water! It can cause itchy skin and burning eyes. You can read more on this in a recent article here on my website. There’s 1 possible danger that could actually require medical attention.

Just click on the link to read it on my site.

How long does it take to raise the pH in a hot tub?

As a general rule, after adding a spa up or pH increaser, it will take approximately 20 minutes to see an increase on a test strip. Ensure the jets and water features are on and the cover is off for maximum efficiency.

If you have been neglecting your maintenance duties and only just realized that the pH is low, you have some work to do before you can safely say it’s ok to use your hot tub.

How long this takes depends on how much baking soda you need to add, and this, in turn, depends on several factors:

  • How much water is in your hot tub?
  • The pH level of the water
  • The total alkalinity of the water

If you’re not sure how much water is in your hot tub, just measure the surface area and multiply this by the actual depth of water. 1,000 cubic inches = 4.33 gallons, so if your tub measures 65” x 60” x 30” inches, that’s 117,000 cubic inches, so your tub holds 506.6 gallons.

Next, you need to check the pH level.

If it’s only slightly low, say 7.0ppm, you only need enough to raise the level by 0.2ppm. Don’t forget, adding baking soda raises the alkalinity too, so you don’t want to overdo things.

Using the formula 0.16oz of baking soda per 100 gallons of water for a 0.2 rise in pH, this particular tub will need 5.07 x 0.16 = 0.8oz, say 2 tablespoons of soda.

Then follow these steps:

  1. Turn off the equipment
  2. Add the required amount of baking soda
  3. Turn the pump on and let the jets circulate the water for a couple of hours
  4. After this time, re-test the water
  5. If the pH is still too low, repeat steps 1-4 using half the initial dosage

If the pH is at or above 7.2 after stage 4, then that’s it. You’re all set to go. The whole process takes 2 to 3 hours.

Spa-up vs. baking soda to raise pH: which is better?

Generally, spa-up or pH-up products will produce better results with a smaller amount as baking soda only marginally raises pH. However, if the pH is just a little low but alkalinity needs to come up also, baking soda can work well.

But there are 2 things to consider when deciding which route to go down: cost and the amount needed to increase the pH enough.

First, let’s compare the cost. A 2lb bottle of Spa Up on Amazon costs around $12 ($6 per pound), whereas a 5lb bag of pure baking soda such as that marketed under the brand Cesco on Amazon costs $20 ($4 per pound). That’s quite a difference.

But you can check the latest prices on Amazon by clicking on the links.

The amount needed to raise the pH depends on how low the level has dropped, but in comparing the options, it is safe to use an amount necessary to raise the pH by 0.1ppm. Spa Up requires 1 ounce for every 500 gallons until reaching the optimum level.

Better to add too little than to add too much. It is easy to add more, but once it is in your hot tub, you can’t take it away. You must add more chemicals such as sodium bisulfate to get the level back down again.

The application of both Spa Up and baking soda is the same – you just sprinkle the powder over the surface. They will both dissolve quickly, and there is no need to wait before getting in the water once the pH level is back within range.

But the bottom line is this. Spa Up is composed of 100% sodium bicarbonate. So it is, by and large, the same thing.

So, if you want to pay 50% more for a brand name, go right ahead.

Final Thoughts

If you’ve learned one thing from this, it is that baking powder is NOT the best thing to use to raise pH in your hot tub.

If the alkalinity is very low and you just want to raise the pH a little, then baking soda is fine. However, if you want to drastically increase the pH without affecting the alkalinity too much, then soda ash is the best product to use.

If there is anything I missed, or you have any questions on this subject, just drop me a line, and I will do my best to answer it. And don’t forget to check out the other related articles here on my site.

Just click on the links.

Ready to Spend Less Time On Maintenance and More Time Enjoying Your Hot Tub?

Let’s face it. Balancing the water, cleaning filters, dealing with rashes, and trying to figure out which chemicals to buy and add can make you feel more like a chemist than someone who just wants to relax after a long hard day!

That’s exactly why The Hot Tub Handbook and Video Course is so valuable!

This is from Matt over at Swim University and he developed it for people looking to save money, time, and frustration. His tips on chemicals can save you $100/year just by making sure you buy only what you need.

So if you’re ready to stop being confused or frustrated with your hot tub and start spending more time in it, check out The Hot Tub Handbook and Video Course.

Just click that link to learn more on their website.

Image by NatureFriend from Pixabay

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Jeff Campbell
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