How Much Baking Soda To Raise Alkalinity In A Hot Tub?

How much baking soda to raise alkalinity in a hot tub?

If you want to give your hot tub alkalinity levels a boost, there’s an easy solution: bicarbonate of soda! But how much baking soda does it take to raise alkalinity in a hot tub?

There is a simple way – keep testing, follow the method below, and see. But why leave it at that?

Some background knowledge about how your tub water’s alkalinity and pH levels are tied together will save you some serious hassle and stand you in good stead in the future.

Here’s everything you need to know:

Understanding pH Level And Alkalinity

As most of us will vaguely remember from school science class, pH level is a measure of how acidic or alkaline something is. In this case, the water in your hot tub.

This means that the Total Alkalinity (TA) and pH levels of your water are directly tied together:

  • If you have low pH, your water is too acidic
  • If you have high pH, your water is too alkaline

Neither of these is a good outcome. Both pH levels that are too low and those that are too high can result in problems ranging from itchy skin and eyes to bacteria growth. At the worst levels, you’ll even cause physical damage to your tub.

So what can we do to make sure these problems don’t occur?

What Happens If Alkalinity Is Too Low In A Hot Tub?

Many things will lower your hot tub’s Total Alkalinity. This includes every time someone gets into your tub. Everyone sweats and has body oils, not to mention often being covered in beauty products and the like. If your tub is outside and uncovered, enough rainwater can have an effect too.

Of course, as we now know, alkalinity and acidity are tied together. This means that low alkaline levels naturally mean your hot tub water is more acidic, resulting in those bad outcomes we touched on above:

  1. Sanitisation problems – with low alkalinity, sanitising chemicals (bromine and chlorine) become less effective. They may also work unpredictably.
  2. Tub damage – too much acidity can stain, crack, and pit even the tough acrylic surface of your tub as well as corrode internal components that are not cheap to replace.
  3. Person damage – you and your fellow bathers are not going to enjoy the skin complaints and eye irritation that low alkalinity causes.

What Is Total Alkalinity And Why Is It Important?

Total Alkalinity is the measurement of the quantity of alkaline chemicals in your hot tub water.

Alkalinity is helpful because it essentially balances out any acidity present.

TA can in fact sometimes be thought of as a buffer or cushion for hot tub water health. This is because having a good TA level will help to even out any potential peaks and troughs in your pH level (you’ll sometime see this called a “pH bounce” and it’s a real pain).

In short, Total Alkalinity is important for your hot tub water chemical balance because it:

  1. Balances out any acidity that is present
  2. Helps maintain a steady pH level
  3. Avoids pH bounce and other difficulties in creating that steady pH

This means that if you’re trying to achieve a good steady pH level in the target zone, you should aim to achieve a good TA level first.

Will Baking Soda Raise Alkalinity In A Hot Tub?

Yes. Baking soda is one of the best ways to raise your hot tub’s alkalinity and its pH level. You should be aiming for:

  • pH level of between 7.2 and 7.8 (7 is pH neutral)
  • Total Alkalinity of between 80 and 120 parts per million

How To Increase Alkalinity In A Hot Tub Using Baking Soda

  1. Test Total Alkalinity and pH – before you start, it’s a good idea to know where you’re at. Buy some hot tub test strips and check your levels.
  2. Determine size of tub – work out how much water your tub can hold. Most four-person tubs are around 300 gallons in size.
  3. Add baking soda – a rough guideline is often said to be one tablespoon of baking soda per 100 gallons. For a four-person tub, this means three tablespoons might be a good estimate. Bear in mind that you might need less if you’re nearly in the target zone.
  4. Wait – it can take a little while for the baking soda to raise that alkalinity. Go do something else for a bit before testing those levels again.

How Long Does It Take For Baking Soda To Raise Alkalinity In A Hot Tub?

Even with your hot tub water jets on, it will take around two to four hours before the baking soda affects your TA.

Is Alkalinity Increaser Better Than Baking Soda?

You can buy a specially designed “alkalinity increaser”. However, this product tends to be made of soda ash – something that is a bit more neutral than it is alkaline. This means:

  1. If you have good pH but bad TA – use baking soda. It’ll raise your TA a lot without affecting your pH so much.
  2. If you have bad pH but okay TA – use soda ash. This will raise your pH without giving you an unbalancing boost of TA.

Need To Know More About Hot Tub Chemical Balance and Other Maintenance Tips?

Sign up for our FREE newsletter or alerts for more advice from hot tubbers, for hot tubbers!