What Causes High Alkalinity In the Hot Tub [Solutions]

Alkalinity is an irritating issue in a bathtub that discourages you from having a nice bath in the tub. Simply, it makes your bathtub water cloudy and green and not suitable for taking a bath.

Generally, alkalinity in water destroys the sanitizer elements like chlorine, bromine, etc. in your bathtub. As a result, the water loses its natural color, and sometimes it becomes unhealthy as well.

At this point, you must be thinking about what causes high alkalinity in the hot tub, right? A lot of unnatural factors, like too many chemicals, sweat, body wash, lotion, etc., can cause high alkalinity in your hot tub water.

However, this is not a common hot tub issue, and once your tub is affected, it would be difficult to deal with it. But if you have a clear idea of this concept, you might understand what to do.

What is Alkalinity?

Usually, the alkalinity of the hot tub water indicates its buffering capacity against changes in pH. To be more specific, alkalinity in the hot tub measures the ability of the water to resist changes in pH.

It simply represents the concentration of alkaline substances, including hydroxide molecules and dissolved calcium, in the hot tub water. You can measure in parts per million (ppm) or milligrams per liter (mg/L) of calcium carbonate (CaCO3).

This concept is closely related to the pH of the water. Initially, the stabilizer for pH in hot tub water is the same thing as its alkalinity level. Being aware of alkalinity is essential, especially to maintain the pH level in the hot tub water.

The recommended alkalinity level by the National Pools& Spas Association for hot tub water should be between 80 and 120 parts per million (ppm) or 80 to 120 milligrams per liter (mg/L). This measurement can vary according to the hot tub manufacturer’s guide and the quality of water you are using in the hot tub.

What Causes High Alkalinity in Hot Tubs?

Just as I said before, alkalinity is not a regular issue you can see in your hot tub. And it doesn’t usually happen for natural reasons. There must be some unnatural factors that trigger the water to raise its alkalinity.

Here are some possible factors that are effective in this context:

Water Source Issue

The water source in your bathtub can determine the quality of the water. There are some elements, like bicarbonate, that can raise the alkalinity of water.

So, if the water source contains high levels of bicarbonates, your hot tub water might have a higher alkalinity. And that’s the most common case in this fact.

However, there are some regions that have naturally high alkalinity in water supply. So, it can automatically affect your hot tub water and raise alkalinity.

Overuse of chemicals

There are a lot of bathtub maintenance products and bath supplies that are rich in sodium bicarbonate or baking soda. These elements work effectively to raise the alkalinity level in the hot tub.

Eventually, this can lead to excessive levels if the use of those elements is not maintained. Oftentimes, some non-brand tub cleaning agents contain so many alkalic elements that they do not even mention them.

baking soda for pH level adjustment

pH Imbalances Issue

Sometimes, it’s not an issue regarding the chemical or the water source. Imbalances in pH and calcium hardness can also affect alkalinity levels in your hot tub water.

You need to remember that the concepts of alkalinity and pH are closely related. Indeed, high pH levels or calcium hardness can result in increased alkalinity over time.

Sudden Increase of Carbonates and Bicarbonates

Oftentimes, your hot water tub gets a sudden increase in carbonates and bicarbonates, which results in a higher level of alkalinity. Especially when hot tub water evaporates from the tub, the dissolved carbonates and bicarbonates become more concentrated. 

If the water is regularly topped up without proper water replacement and dilution, the concentration of these alkaline substances can gradually increase, leading to higher alkalinity levels.

Chemical Reaction Issue

It’s not uncommon for your hot tub water to contain different types of chemical agents. And when you add an external one, it can cause a reaction that increases the level of alkalinity in the water.

This type of reaction happens when we add an acidic chemical to the bathtub water without acknowledging the level of pH, the insoluble calcium, or the presence of other chemicals in it.

Besides, our bodily sweat, excessive use of body wash, lotions, and additional bathing cosmetics can be reasons to raise the alkalinity level in the hot tub.

Effects of High Alkalinity in a Hot Tub

At this point, you must be thinking about what exactly can happen if the hot tub water has a higher level of alkalinity. Well, the aftermath is pretty irritating. Indeed, high alkalinity in hot tub water can cause a number of problems.

  • Increases the pH level of the water to rise above the optimal range.
  • Scale builds up on the surfaces of your hot tub, which makes it difficult to clean the tub.
  • Results in skin irritation for the people who use your hot tub.
  • Makes the water in your hot tub cloudy, which can make it unpleasant to use.
  • This makes it difficult for the sanitizers to work effectively.
  • Increases the growth of bacteria and algae in your hot tub.
  • Causes eye irritation and hair damage.

Effective Solutions for Hot Tubs with High Alkalinity

There are a few DIY tips that work effectively to reduce and adjust the alkalinity level in your hot tub water. You can follow the tips below. But first, you need to test the water to know whether it needs to be adjusted for alkalinity.

For that, you can use a reliable test kit or test strips that are specifically designed for hot tubs. The ideal range for alkalinity in a hot tub is typically between 80 and 120 parts per million (ppm). So, if it’s more than 120 ppm, you need to decrease the level.

  • Use a store-bought pH or alkalinity decreaser and use it following the instructions in the manual. You can try Pool Mate 1-2607I.
  • Try baking powder applications to reduce the alkalinity level.
  • Keep circulating the water for 30 minutes without a pause.
  • Ensure a safe water source.
  • Make sure to use safe cleaning agents and cosmetics.

You need to retest the water after applying any process. But if you manage to maintain the tub well and use an appropriate cleaning agent, you will have fewer chances of seeing this type of problem.

Frequently Asked Questions

How do I test the alkalinity level of the hot tub water?

You can test the alkalinity level in the hot tub water by using an alkalinity test kit. You can use Poolmaster 22212 Smart Spa Water Chemistry Test Strips.

After how long should I test the alkalinity level in my hot tub water?

You should test the alkalinity level in the hot tub water 3 to 4 times every month. The level constantly changes, and that’s why you need to taste it frequently.

Can my hot tub water have a lower alkalinity level?

Yes, your hot tub water can have a lower alkalinity level, especially when the pH level drops.

Wrapping Up

Testing the level of alkalinity is not a big deal. But if you manage to do it regularly, you can save yourself and your tub from many big issues.

Besides, the level of pH and alkalinity can change overnight. And you shouldn’t use the tub when the level is not okay.

Hopefully, you have gotten my point. Comment in the below section for any further inquiries. Thank you for your time.


Hi, I'm Shimul, the founder of Pooltub Life. I'm excited about sharing the latest outdoor living trends with you. My goal is to provide you with up-to-date information that will help make your POOL & HOT TUB stylish and enjoyable. Read About Me More । Follow on Facebook

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