One of the most important parts of hot tub maintenance is maintaining proper pH and alkalinity levels. When the pH of a hot tub is too low, problems like metal corrosion, high bacteria levels, and eye burns can occur.

Why is hot tub PH important?

The pH value is an index used to measure the acidity and alkalinity of a solution, and it indicates the concentration of hydrogen ions in the solution. The pH scale ranges from 0 to 14, where 7 is neutral, below 7 is acidic, and above 7 is alkaline. pH testing plays an important role in multiple industries, helping to monitor and control acidity and alkalinity, maintain product quality, and protect the health of the environment and ecosystems.For hot tubs, pH value is very important because it has a direct impact on water balance and user experience. A good pH in a hot tub is usually between 7.2 and 7.8.

pH test strips for testing pH
pH test strips for testing pH

The Importance of PH to Hot Tub Water Quality

  1. Water Balance: Proper pH helps keep your hot tub water balanced. A pH that is too high or too low can cause water quality problems such as corrosion or scaling.
  2. User health and comfort: The correct pH value can provide a comfortable soaking experience and avoid irritation to the skin and eyes. A pH that is too high or too low may cause dry, itchy or stinging skin.
  3. Water treatment effect: Appropriate pH value contributes to the effect of disinfection and water treatment chemicals. If the pH is too high or too low, the sanitizer can become ineffective, affecting the cleanliness and sanitation of the water.
  4. Equipment protection: Proper pH helps protect the durability and functionality of the equipment inside the hot tub. A pH that is too high or too low can cause corrosion, clogging or damage to equipment.
Feel the heat and comfort of the bathtub with your hands
Feel the heat and comfort of the bathtub with your hands

Maintaining a proper pH level is critical to hot tub water quality, user health, and equipment protection. Regularly testing and adjusting the pH of your hot tub is a critical step in maintaining a good soaking experience and water quality management.

What is alkalinity?

Alkalinity is a measure of the amount of alkaline substances (bases) in a solution. It measures the availability of hydrogen ions (H+) in a solution. Alkalinity is distinguished from pH, which primarily measures the concentration of hydrogen ions in a solution, whereas alkalinity focuses on the amount of alkaline substances in a solution that can neutralize acidity.

Alkalinity is usually used to measure the concentration of alkaline substances such as carbonates, hydroxides, and bicarbonates in water. It is expressed in terms of alkalinity, and the common unit is mg/L or ppm (parts per million).

In a hot tub, it is very important to know the alkalinity of the water. Proper alkalinity helps maintain the balance of water quality and ensures that the water quality is in an ideal state. The control of alkalinity can help adjust the pH value and avoid the water quality from being too acidic or alkaline, thus providing users with a comfortable soaking experience.

Low Or High PH In The Hot Tub

When a hot tub has a low or high pH, it can negatively impact the water quality and experience.

pH is too low

  • Increased Corrosivity: Water with a low pH is more acidic and can cause corrosion and damage to metal parts such as pipes, pumps, etc.
  • Increased irritation: Acidic water can be irritating to the skin and eyes, making the bath experience uncomfortable.
  • Unstable water quality: Low pH levels make water unstable, causing cloudiness, odor, and an increased risk of bacterial and algae growth.

pH is too high

  • Increased Corrosivity: High pH water is more alkaline and can cause corrosion and damage to metal parts.
  • Unstable water quality: A high pH can cause the water to become cloudy and allow calcium and magnesium ions in the water to precipitate, forming scale.
  • Skin Irritation: Alkaline water may cause skin dryness, stinging and discomfort.

Regularly testing and adjusting the pH of your hot tub can be done with the use of a pH testing kit and the proper water treatment chemicals. Apure A10 pH orp controller is a good choice for most testing needs.

Why do hot tubs have a low PH?

  • Acidic Additives: Certain water treatment chemicals or acidic additives, such as pickling agents, cleaners, etc., can be mistakenly added to the hot tub, causing the pH to drop.
  • Water issues: If you are using tap water or the water itself has a low pH, the pH in the heated hot tub will drop accordingly.
  • Acid Contaminants: Hot tubs can become contaminated by outside elements such as leaves, dirt, or other acidic substances entering the water, causing the pH to drop.
  • Improper use of chemicals: Using improper or wrong water treatment chemicals, cleaners, disinfectants, etc., can negatively affect the pH of your hot tub, causing it to lower.
  • Improper drainage and make-up water treatment: Improper treatment of drain and make-up water in a hot tub, such as water entering the hot tub without proper filtration or treatment, can lead to a drop in pH.

If the pH of the hot tub is found to be lower than the ideal range, it should be tested and adjusted in time, and appropriate measures should be taken to resolve the problem that caused the pH drop.

Raising or Lowering The pH of Your Hot Tub

To raise or lower the pH of your hot tub, do the following:

  1. Use a pH increaser: Buy chemicals that are specifically designed to increase or decrease the value, such as alkaline chemicals or raising agents. Follow the product instructions, gradually add the appropriate amount of pH increaser to the hot tub, then stir or circulate the water well to distribute it evenly.
  2. Use a pH lowering agent: Purchase chemicals that are specifically designed to lower the value, such as acidic chemicals or lowering agents. Follow the product instructions, gradually add the appropriate amount of pH lowering agent to the hot tub, then stir or circulate the water well to distribute it evenly.
  3. Add alkaline substances: If you don’t want to use chemicals, you can consider adding some common alkaline substances to increase the pH. For example, baking soda (sodium bicarbonate) is a common alkaline substance that can be added gradually to a hot tub. Make sure to dissolve it well before adding to avoid precipitation in the water.
  4. Add Acids: Similarly, consider adding some common acids to lower the pH. For example, acetic acid or lemon juice are common acids that can be added gradually to a hot tub. Make sure to dilute it well before adding it to avoid overly impacting the water quality.
  5. Adjust your water source: If your water source has an inherently low or high pH, try filling your hot tub with water that is more alkaline (raises the pH) or more acidic (lowers the pH). to raise or lower the overall pH. This may require contacting the water supply company or using proper water treatment equipment.

Alkalinity should always be adjusted first to the 80-100 ppm range, followed by pH adjustment to the ideal range of 7.2 to 7.8. Whether you are raising or lowering the pH of your hot tub, you need to do it with care and follow the product instructions or professional advice for proper treatment. It is best to wait a period of time after adjusting the pH, then retest and make any necessary adjustments to ensure the desired pH level is achieved.

Plastic pill bottles next to bathroom sink in modern bright bathroom
Plastic pill bottles next to bathroom sink in modern bright bathroom

PH And Other Water Quality Parameters In Hot Tubs

ParameterReference RangeEffect
pH7.2 – 7.8Measure the acidity and alkalinity of water, too high or too low may cause discomfort or damage to skin and equipment
Temperature36 – 40°CMake sure the hot tub provides a comfortable temperature
Water Hardness100 – 300 ppmMeasures calcium and magnesium levels in water, high hardness water can lead to scaling and equipment damage
Free Chlorine1 – 3 ppmIndicates the amount of chlorine in the water, used to kill bacteria and keep the water hygienic
Free Bromine2 – 4 ppmIndicates bromine content in water, used to kill bacteria and keep water hygienic
Total Dissolved Solids(TDS)1000 – 2000 ppmIndicates the content of total dissolved solids (TDS) in water, high concentrations may affect water quality and equipment performance
Alkalinity80 – 120 ppmMeasures the content of alkaline substances in water, which affects the pH value and acid-base balance of water
Nitrate0 – 10 ppmIndicates the level of nitrates in the water, too high may have negative health effects
Phosphate0 – 10 ppmIndicates the phosphate level in the water, too high may cause scaling and water quality problems
Copper< 0.3 ppmIndicates the copper content in water, high concentrations may have adverse effects on equipment and water quality
ph and other water quality parameters in hot tubs table

Testing Your Hot Tub pH

How to Test Hot Tub pH?

  1. Prepare your testing kit: Get a water testing kit for your hot tub, such as test strips or an electronic water tester. Make sure the testing tools are accurate and reliable.
  2. Obtaining a Water Sample: Using an appropriate container, collect a water sample from the hot tub. Ensure that there is no contamination from other substances during sampling.
  3. To perform the test: Insert the test tool into the water sample or dip the test strip into the water sample according to the test tool’s instructions. Wait for a while until the test tool displays the results.
  4. Record Results: Read and record results for pH and other water quality parameters as directed by the test kit. Ensure accurate recording and tracking of changes in water quality parameters.
  5. Take action on the results: Based on the test results, decide if further adjustments to the water quality are required. If adjustment is required, increase or decrease pH or other parameters appropriately according to the methods mentioned earlier.

Depending on the specific hot tub type and the recommendations of a professional, the method of testing and adjusting the water may vary.

Testing Hot Tub Water Quality Instruments

  1. Ph value: PH meter is an instrument specially designed to measure pH, which uses electrodes to measure the concentration of hydrogen ions in water and convert it to pH. A pH meter usually has a digital display and an electrode plug to measure pH quickly and accurately.
  2. Free Chlorine: Use free chlorine meter to measure the free chlorine content. A chlorine meter provides more accurate measurements, while a chlorine kit is a convenient test tool for a quick test.
  3. Free Bromine: Use bromine analyzer or a bromine kit to measure the free bromine content. Bromine Meters provide accurate measurements and Bromine Kits are an easy-to-use testing tool.
  4. Alkalinity: Alkalinity is measured using an alkalinity meter or an acid-base titrator. These instruments measure the amount of alkaline substances in the water, such as the concentration of sodium hydroxide or sodium bicarbonate.
  5. Salinity: Use salinity meter to measure salinity. A salinity meter measures the salinity in water, which is the amount of dissolved salt in the water.
  6. Conductivity: Conductivity meter usually cannot be used directly to determine the pH of a hot tub. However, it is important in testing hot tub water quality monitoring, which can help evaluate the dissolved content and ion concentration in water, and has certain reference value for judging water salinity, concentration changes and the overall condition of water quality.

These instruments can be selected according to specific test needs and accuracy requirements. When performing tests, be sure to follow the operating instructions of the instrument and pay attention to the correctness and accuracy of calibrating and maintaining the instrument.

How to keep metal and other impurities from entering the hot tub?

  • Install a filter: Installing a filter on the water inlet line of the hot tub can effectively filter out suspended particles and impurities in the water, including metal particles and solid impurities. Choose the appropriate filter type and level, and clean or replace the filter regularly.
  • Use a water treatment agent: Using an appropriate water treatment agent can help prevent metal deposition and corrosion, thereby reducing the release of metal ions. For example, using anti-metal deposits and anti-corrosion agents can protect hot tub plumbing and equipment from metal ions entering the water.
  • Regular cleaning and maintenance: Regularly clean the interior and exterior surfaces of your hot tub, including plumbing and equipment. Removes built-up dirt, scale and impurities before they get into the hot tub water. Note that the frequency of cleaning and maintenance should be adjusted according to the frequency of use and water quality.
  • Control your water source: Choosing a high-quality water source can reduce the levels of metals and other impurities. If the water quality is poor, consider using water treatment equipment, such as a reverse osmosis system or water softener, to purify and improve the water quality.
  • Regularly test water quality: Regularly test the water quality of the hot tub, including parameters such as pH level, alkalinity, metal ion content, etc. According to the test results, take corresponding measures for adjustment and treatment to ensure that the water quality meets safety and hygiene standards.


Properly adjusting and maintaining the pH of your hot tub is critical to water hygiene, comfort, and protection of your equipment. Regularly monitoring and adjusting pH, along with other water quality parameters, is an important part of keeping your hot tub water in good condition. How to choose a pH test instrument is very important. Apure has many options to meet your needs for testing in different occasions. Please contact our professional technical team to provide you with solutions.

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