Using Soda To Raise Hot Tub Alkalinity? [September 2020]


Raising your hot tub’s alkalinity is different than just making it more basic or less acidic. I will try to explain how to raise the total concentration of alkaloids within the water, which is the proper way to do it. The most common types of alkaloids you can find in your hot tub water are carbonates, hydroxides, bicarbonates, and other minor alkaloids.

In order to raise your hot tub alkalinity, you should add 1 tbsp of baking soda to the hot tub for every 100 gallons of water it holds. Then turn on the hot tub jets and have the water circulate along with the baking soda from 2 to 4 hours. Keep switching between circulating and adding baking soda to the water until the pH level gets within the range of 7.2 to 7.8.

But first, if you are not aware of what these terms actually mean, let’s remind ourselves and try to answer more questions about alkalinity altogether.

What Is Total Alkalinity And How It Is Different From pH Level

Before we go deeper into the topic, there is one thing we should really make clear. Your total alkalinity and pH, when put together, are actually two very different things. 

The regular tap water we know today is (opposite of acidic) called “alkaline”. There are often misconceptions about these terms that so often get people confused, even those in the industry. 

To put it simply, pH is a relative measure of a solution’s alkalinity as it relates to water. On the other hand, a term “total alkalinity” (TA) measures the total number of alkaloids within a solution’s sampled volume.

Now that we know that total alkalinity is different from pH levels, meaning that total alkalinity isn’t a relative measure, but a measure of all alkaline chemicals that are dissolved in a sample (such as water). Total alkalinity will usually represent the concentration of hydroxides, carbonates, bicarbonates, and other alkaloids within your sample (of water). 

When it comes to measuring the two, total alkalinity is measured in a different way than pH ranges. Total alkalinity is actually measured in parts per million (ppm), which you could have come across in other posts, unlike the relative pH ratings. 

Having a higher concentration of alkaloids means that your hot tub’s pH will become more stable since it requires more of a given substance in order to change its concentration of alkaloids. Understanding these concepts, we can say that it is totally possible to have hot tub’s water pH balanced while still having issues with alkalinity.

How Do I Test The Alkalinity In My Hot Tub

You certainly want to use the test strips. For those who don’t know, pH and total alkalinity test strips are a single test strip that just has two separate test pads, one for pH and the other for total alkalinity. 

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The test strips are a simple alternative to wet chemical tests since they will give reproducible results for each test separately. 

Look at the test ranges for each parameter:

pH6.0 – 9.0
Total Alkalinity0 – 360 ppm

How To Use The Test Strips

Follow the steps and tips below in order to get as accurate readings as possible

  1. You should dip one test strip into a water sample for 10 seconds and then remove it.
  2. Immediately match the pH test pad color
  3. Match the total alkalinity test pad color. 
  4. It’s a simple test with no chemicals to mix. Your results are obtained in 30 seconds
  5. The test strips are safe to use, with no hazardous chemicals

Is Low Alkalinity Bad In A Hot Tub

If your alkalinity level is too low, then your hot tub pH can fluctuate pretty bad even at the slightest addition of an acid or base. 

This can cause the pH to drop randomly, which then causes damage to the hot tub shell, metal surfaces, and it will be bad for all the users as well. 

Therefore, it is really important to run routinely tests and generally it is recommended to take at least one test a week. 

As we said, low total alkalinity is also bad for your hot tub’s various components. The surface of the shell usually becomes etched, pitted, having the protecting layer of the shell delaminated. 

Any metal parts that come into contact with water having low total alkalinity can cause corrosion, putting your heating elements, heaters, and pipes at risk. Additionally, it can cause calcium scaling, making it more difficult to keep surfaces clean and plumbing free of scale buildup.

Will Alkalinity Increaser Raise pH

Alkalinity increaser is sodium bicarbonate (which is also called sodium hydrogen carbonate). Its main job is to raise Total Alkalinity. Alkalinity increaser has a pH of only 8.3, which will increase overall pH levels, but only if they were extremely low. However, when it comes to the general impact on pH, it will certainly have a lesser effect on overall pH.

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What Causes Low Alkalinity In Hot Tub

If you would have two choose between the two extremes, low alkalinity is for sure the more serious of the two. It can cause quick fluctuations in pH, because then the water is not able to counteract the effects of acids, such as acid rain or naturally occurring minerals. 

Such an environment has a number of effects on the appearance of your spa: it can damage and erode its surfaces while corroding metal parts, a perfect storm can lead to unattractive stains. Low alkaline water will also not be able to balance the amount of phosphate that algae feed on, resulting in green water.

Both MPS and Dichlor are net acidic after considering their consumption, so you will definitely have a TA drop in this situation over time (it’s just like adding acid to your spa) and need to add either baking soda or pH Up to bring it back to where it was.  The only thing that a certain TA value brings in this situation is relative pH stability.  

That is, at a certain TA level, the rate of pH increase due to carbon dioxide outgassing can be equal to the rate of pH decrease from the net acid sources of chlorine or oxidizing agent. 7 tablespoons MPS and 1 tablespoon dichlor (i.e. one week of chemical use) would require 2.6 tablespoons baking powder to compensate for the decrease in TA, provided that the carbon dioxide outgassing kept the pH constant.  

You need to add more because there is not enough carbon dioxide outgassing so that the pH decreases slightly.  At a higher TA level, you can achieve this pH balance, but you need to add something to restore the TA (carbonates lost as carbon dioxide). It is when you use a hypochlorite source of chlorine that the TA is fairly stable and where a lower TA to minimize carbon dioxide outgassing makes the pH more stable.

Should I Raise pH Or Alkalinity First

Your total alkalinity (TA) and pH will move together. The trick is to get your pH in line first, then raise total alkalinity a bit higher than you want it and SLOWLY lower the pH back down. 

This should get your total alkalinity where you want it to be. In addition, the constant aeration in a spa causes total alkalinity to go down because of the gassing off of CO2. 

This explanation is pretty technical but the solution is not that hard. And realize that you will possibly have to be adjusting total alkalinity at regular intervals. Keep track of your testing results and soon you will learn how high to raise the total alkalinity so it is in line once you adjust your pH back down.

How Much Baking Soda Does It Take To Increase Alkalinity

Researcher and author Dr. Robert O. Young has been researching the importance of pH balance for over two decades now. He has been looking for different ways to increase the alkaline levels by adding an alkaline ingredient to your water. 

Dr. Young recommends simply adding a half a teaspoon of baking soda to a gallon of water and mixing it vigorously to ensure it mixes in completely. Since baking soda is highly alkaline, adding only a small amount to your purified water will result in a gallon of alkaline water.

Depending on how much water can your hot tub hold, you can easily calculate the amount of baking soda you will need.

It is important to state that you should continue to test your pH levels as you are adding soda and mixing your water.

Is It Safe To Bath With Low Alkalinity

The term pH means the “power of hydrogen,” and it’s measured on a scale that goes from 0 to 14. When you measure your pH level and it shows that it is higher than 7, which is neutral, then the water is alkaline. That means it has an excess of negative hydroxide ions. 

In case your water test shows a pH level below 7, then that means that the water is acidic, meaning it has a surplus of positive hydrogen ions. 

The pH scale is logarithmic, so hot tub water with a pH of 6 is 10 times more acidic than water with a pH of 7. Following the math, hot tub water with a pH of 5 is a hundred times more acidic than the pH 7 one.

Now that I have explained the math, when the pH is low, meaning the water is acidic, swimmers could suffer from itchy skin, rashes, burning eyes, and dry hair. 

The hot tub and all its components can suffer, too, since acidic water can corrode shell, metal accessories, and machinery in the water circulation and purification system. 

In addition, free chlorine levels become unpredictable and extremely difficult to maintain in acidic water. Despite all of the above, it’s usually still safe to spend time in your hot tub. It just might not be as comfortable.

How Does Rain Affect Hot Tub Alkalinity

Rainwater is known to be acidic so it definitely doesn’t help with maintaining the proper pH level of your hot tub water. You should always cover your hot tub when raining.

When rainwater enters the hot tub, it can change your water’s pH, alkalinity, calcium hardness, total dissolved solids (TDS) and other chemical levels as well as bring contaminants (e.g. debris, dirt) into the hot tub. This will obviously depend on where your hot tub is placed and whether there is a chance for extra dirt to enter the hot tub  

Since rainwater is generally acidic, then your hot tub water can become corrosive and cause damage to the shell and metal parts of your hot tub. The extent of the chemistry issues you’ll experience will largely depend on how much rain pours in your hot tub. 

For example, light rain, should not really have any effect on your hot tub water. Although, you should always be certain that your hot tub water chemistry is properly balanced at all times.

Will High Alkalinity Make Hot Tub Cloudy

If you test your hot tub water for total alkalinity and it shows high levels of alkalinity, excess of carbonates can make the hot tub cloudy. High total alkalinity levels will also make it hard to control your pH level and keep it in check. 

You should use pH decreaser in order to lower total alkalinity to around 100 ppm. In case your hot tub pH level is outside of the range of 7.2 to 7.6, adjust accordingly for easier control of cloudy water.

Does Shocking Hot Tub Raise pH

You know that every once in awhile, in order to clear your hot tub of any cloudiness and contaminants, you should shock your water. Let’s remind ourselves about the chemical normal levels that should be maintained in your hot tub at all times. Any of those that measure outside of the given range should be fixed.

ChemicalLowHigh
Alkalinity80120
pH7.27.8
Chlorine1.53.0
Bromine3.0 5.0

Shocking your hot tub will certainly balance your pH levels and not raise it. Again, all of these chemicals are related and can cause one to raise another. Make sure you perform enough tests before jumping in the hot tub.

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Editorial Staff

I'm Adnan Sabanovic, the guy behind Hot Tubs Report. I've had a chance to enjoy hot tubs last few years and have really become interested in owning one of them. Nearly every weekend you'll find me spending time with my family or playing sports. If I am not doing that then I'm here writing about tubs on Hot Tubs Report. This blog is a research for my first hot tub which I decided to document and share publically so others can benefit from it as well.

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