How to Lower Alkalinity in Hot Tub and Prevent Skin Irritation

High alkalinity levels can make your hot tub water cloudy, foamy, and irritating to your skin and eyes. That’s not what you want from a relaxing soak, is it? But don’t give up on your hot tub yet. Low alkalinity in the hot tub can be restored with a few simple steps.We are going to share with you a few simple and effective tips for lowering alkalinity in your hot tub in no time.These tips will simplify your hot tub maintenance, regardless of whether you’re a newbie or a seasoned pro.Join us on this journey and learn how to achieve a perfect hot tub experience.

What’s the Optimal Alkalinity Level for Your Hot Tub?

The ideal alkalinity level for a hot tub is between 80 and 120 parts per million (ppm). This range is recommended by most hot tub manufacturers and experts. If the alkalinity level is within this range, the water will be stable and comfortable for you and your spa.

However, if the alkalinity level is too high or too low, it can cause various problems for your hot tub and your health. Let’s see what these problems are and how to avoid them.

What Are the Problems of High Alkalinity in Hot Tub?

  • Ineffective sanitizers: Elevated alkalinity levels can diminish the efficacy of chlorine or bromine in eradicating bacteria and viruses from the water.
  • Scale buildup: Increased alkalinity may trigger the precipitation of calcium and magnesium, resulting in the formation of stubborn deposits on the hot tub’s surfaces, pipes, and jets.
  • Cloudy water: Excessive alkalinity can impart a dull and murky appearance to the water, diminishing its clarity and overall appeal.
  • Skin irritation: High alkalinity can elevate the water’s pH level, causing it to feel harsh and abrasive on the skin. This can lead to dryness, itching, and rashes.
  • Eye irritation: Elevated alkalinity levels can also provoke irritation in the eyes, manifesting as redness, swelling, and soreness.
  • Green water: Low alkalinity levels can cause the water’s pH to drop, creating a conducive environment for algae growth. This can result in green and slimy water.
  • Equipment damage: Insufficient alkalinity may corrode the metal components of the hot tub, including the heater, pump, and filter, potentially leading to leaks and malfunctions.

How Water Hardness and Calcium Levels Affect Alkalinity Balance

Water hardness and calcium levels play a significant role in alkalinity balance in hot tubs. Hard water contains a high level of dissolved minerals, particularly calcium and magnesium, which can contribute to high alkalinity levels. The buildup of mineral deposits from hard water can damage a hot tub’s interior and equipment and require frequent maintenance. Excess calcium can cause your water to become cloudy and make it difficult to maintain balance. Hard water makes it challenging to maintain alkalinity levels.

spa water test strip, Image: Canva

How to Test for Alkalinity in Your Hot Tub?

There are a couple of reliable methods for testing the alkalinity in your hot tub. Each method has its advantages, so let’s explore both options:


1. Test Strips

Test strips are a quick and straightforward way to get an approximate reading of your hot tub’s alkalinity level.


  1. Dip a test strip into the hot tub water for a few seconds, then remove it.
  2. Hold the strip horizontally to let excess water drain off.
  3. Compare the resulting color on the test strip to the provided chart on the package.
  4. Match the color to the corresponding alkalinity level to determine the approximate value.
  5. Record the alkalinity reading for future reference.


  • Simple and easy to use.
  • Provides a quick estimate of alkalinity.
  • No need for additional equipment.


  • May not be as precise as other methods.
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2. Digital Test Kit

Lower Alkalinity in Hot Tub
Testing pool water with a digital meter, Image canva

For more accurate and specific alkalinity readings, a digital test kit is the way to go.


  1. Collect a small sample of hot tub water using the test kit’s sampling tool.
  2. Insert the sample into the designated slot on the digital test kit.
  3. Wait for the device to analyze the sample and display the alkalinity reading on the digital screen.
  4. Take note of the precise alkalinity value for future reference.


  • Provides precise and reliable alkalinity readings.
  • No color matching required, reducing potential errors.
  • Suitable for those who prefer precise water chemistry control.


  • May be more expensive than test strips.
  • Requires occasional battery replacements.

Testing Tips

To ensure accurate and consistent results, consider the following tips:

  1. Take Multiple Samples: Collect water samples from different areas of your hot tub to account for any variations in water chemistry.
  2. Test Regularly: Make a habit of testing your hot tub’s alkalinity regularly, especially after adding chemicals to the water. Frequent testing helps maintain the desired range.
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Lower Alkalinity in Hot Tub
relaxing in hot tub Image: Freepik

What Are the Main Causes of High Alkalinity in Hot Tub Water?

Several factors can cause high alkalinity in hot tub water:

Use of high pH or alkaline chemicals:

If you are using chemicals that are designed to raise the pH or alkalinity of your hot tub water, it can cause the alkalinity to become too high.

Overuse of pH increasers:

If you are using pH increasers too frequently, it can cause the alkalinity to become too high.

Poor water balance:

If the pH, total alkalinity, and calcium hardness levels in your hot tub water are not properly balanced, it can cause the alkalinity to become too high.


If foreign substances such as soap, shampoo, or other contaminants are introduced into the hot tub water, it can cause the alkalinity to become too high.


If your hot tub is leaking, it can cause the alkalinity to become too high as fresh water is introduced into the tub.

Water sources:

Water quality of sources like hard water living area. Water quality is an important factor to consider when living in an area with hard water. Hard water is defined as water that has a high mineral content, usually containing calcium and magnesium.

What Happens If Hot Tub’s Alkalinity Levels Are Too High?

High alkalinity also causes green water, which reduces the efficiency of sanitizers like chlorine and bromine. When the pH levels in your hot tub water are too high, calcium can build up, making the water look cloudy and leading to the formation of scale, which irritates the skin. Also, the water will have an unpleasant odor and flavor. A higher pH also is associated with an increase in biofilm formation.

What Is the Best Way to Lower the Alkalinity in A Hot Tub?

One of the best ways to lower the alkalinity in a hot tub is by using a pH decreaser such as sodium bisulfate or muriatic acid. These chemicals work by neutralizing the excess alkalinity in the water, bringing the alkaline level down to the ideal range of 80-120 ppm. And can be added to your hot tub water according to the instructions on the product label. To use a pH decreaser, follow these steps:

    1. Test the alkalinity of your hot tub water using a water testing kit to determine how much pH reducer you need to add.
    2. Turn off the circulation pump and heater for your hot tub.
    3. Add the recommended amount of pH reducer to your hot tub, following the instructions on the product label.
    4. Turn on the circulation pump and heater, then run the hot tub for at least an hour so the pH reducer can disperse evenly in the water.
    5. Test the alkalinity again to ensure that it is within the ideal range. If the alkalinity remains too high, you may need to apply an extra pH reducer.

It’s important to note that adjusting the pH and alkalinity of your hot tub water can be a delicate process, and it’s best to follow the instructions on the product label and test the water frequently to ensure that the levels are within the ideal range.

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Are There Any Natural Ways to Lower Alkalinity in Hot Tub?

There are a few natural ways to decrease the alkalinity in a hot tub, but it is important to note that these methods may not be as effective as using pH decreasers such as muriatic acid or sodium bisulfate.

One method is by using ascorbic acid, also known as vitamin C, which can help to lower the alkalinity levels in the water. Another option is to use citric acid, which can also help to lower the alkalinity levels.

Another natural method is to add phosphoric acid to the water, which is a natural acid found in many foods and beverages. It can also be used to decrease the alkalinity levels in hot tubs.

Overuse of these natural methods can also cause an increase in pH levels, which can be harmful to the hot tub equipment and the people using it. It’s also important to be careful when handling any chemicals, including natural ones, and to follow the instructions carefully to avoid any potential hazards.

Lower Alkalinity in Hot Tub

Tips for Keeping Your Hot Tub’s Alkalinity Low

  • Testing your hot tub’s alkalinity routinely will alert you to any increases, enabling you to take action before the levels become too high.
  • Use a pH balancer to maintain the pH level of the water in your hot tub to prevent an increase in alkalinity.
  • By draining and refilling your hot tub, you can help reduce the alkalinity in the water.
  • A water softener can help to remove hard minerals from your hot tub water, which can contribute to high alkalinity levels.
  • Properly balancing the chemicals in the hot tub, such as pH, total alkalinity, and chlorine can help to prevent high alkalinity levels.
  • Properly maintaining the hot tub equipment, such as filters and jets, can help to prevent high alkalinity levels.
  • Monitoring the water evaporation and adding water when necessary, to prevent the increase of alkalinity levels.


Lowering alkalinity in hot tub is a must-do for every hot tub owner. It can help you prevent many problems and enjoy a relaxing and refreshing soak. By following the steps and tips we have shared in this blog post, you can lower alkalinity in hot tub easily and safely. You can also use a digital water tester or a smart spa controller to monitor and adjust the alkalinity level and other water parameters automatically. These devices can save you time and hassle and ensure that your water is always balanced and ready for you.

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