Alkalinity is a measure of how well your pool water can resist changes in pH. It is also known as the pH buffer because it helps keep your pH level stable and within the ideal range of 7.2 to 7.8. Having the right alkalinity level is important for your pool’s health, as it prevents problems such as corrosion, scaling, cloudy water, and chlorine inefficiency. In this article, we will explain what alkalinity is, why it matters, and how to test and adjust it in your pool.
What is Alkalinity and Why Does it Matter?
Alkalinity is the total amount of alkaline substances dissolved in your pool water. These substances include carbonates, bicarbonates, hydroxides, and cyanurates. They act as a buffer by absorbing acids that would otherwise lower your pH level. For example, when rainwater or organic matter enters your pool, it introduces acids that can make your water more acidic. Alkalinity neutralizes these acids and keeps your pH from dropping too low.
Alkalinity also helps prevent sharp increases in your pH level by consuming resources that are needed for the pH to rise. For example, when you add soda ash or stabilized chlorine tablets to your pool, you increase the amount of carbonates and cyanurates in your water. These substances can raise your pH level if they are not balanced by alkalinity.
Having the right alkalinity level is important for several reasons:
- It protects your pool surfaces and equipment from corrosion and etching caused by low pH.
- It prevents calcium scaling and cloudy water caused by high pH.
- It maintains the effectiveness of chlorine by keeping the pH within the optimal range.
- It enhances the comfort and safety of swimmers by avoiding irritation to the eyes, skin, and hair.
The ideal alkalinity level for most pools is between 80 and 120 parts per million (ppm). However, this may vary depending on the type of pool surface, sanitizer, and other factors. You should always follow the manufacturer’s recommendations for your specific pool.
How to Test Alkalinity in Your Pool
Testing alkalinity in your pool is easy and inexpensive. You can use either test strips or a liquid test kit to measure the alkalinity level in your pool water. You should test your alkalinity at least once a week, or more often if you notice changes in your water quality or add chemicals to your pool.
To test alkalinity with test strips, follow these steps:
- Dip a test strip into your pool water for a few seconds, following the instructions on the package.
- Compare the color of the test strip with the color chart provided to determine the alkalinity level.
- Record the result and adjust if needed.
To test alkalinity with a liquid test kit, follow these steps:
- Fill a water sample tube with pool water up to the marked line.
- Add a few drops of the alkalinity indicator solution to the tube and swirl to mix.
- The water will turn green if the alkalinity is within range, or red if it is too low.
- If the water is red, add drops of the alkalinity titrant solution one at a time until the color changes to green.
- Count the number of drops you added and multiply by 10 to get the alkalinity level in ppm.
- Record the result and adjust if needed.
How to Adjust Alkalinity in Your Pool
If your alkalinity level is too low or too high, you need to adjust it to bring it back within range. You can use either baking soda or muriatic acid to raise or lower alkalinity in your pool.
To raise alkalinity with baking soda, follow these steps:
- Calculate how much baking soda you need to add based on your pool size and current alkalinity level. You can use an online calculator1 or follow this formula: (Desired Alkalinity – Current Alkalinity) x Pool Volume x 1.5 = Amount of Baking Soda (in ounces).
- Turn off your pool pump and heater.
- Sprinkle the baking soda evenly over the surface of your pool.
- Wait for at least six hours before turning on your pump and heater again.
- Test your alkalinity again and repeat if needed.
To lower alkalinity with muriatic acid, follow these steps:
- Calculate how much muriatic acid you need to add based on your pool size and current alkalinity level. You can use an online calculator1 or follow this formula: (Current Alkalinity – Desired Alkalinity) x Pool Volume x 0.2 = Amount of Muriatic Acid (in fluid ounces).
- Turn off your pool pump and heater.
- Pour the muriatic acid slowly into one spot in front of a return jet.
- Wait for at least six hours before turning on your pump and heater again.
- Test your alkalinity again and repeat if needed.
How to Maintain Alkalinity in Your Pool
Once you have adjusted your alkalinity to the ideal level, you need to maintain it by following these tips:
- Test your alkalinity regularly and adjust as needed.
- Avoid adding chemicals that can affect your alkalinity, such as soda ash, stabilized chlorine tablets, or algaecides. Use alternatives such as borax, liquid chlorine, or non-stabilized chlorine tablets instead.
- Keep your pool clean and free of debris that can introduce acids to your water.
- Cover your pool when not in use to prevent evaporation and rainwater from diluting your water.
By keeping your alkalinity in check, you will ensure that your pool water is clear, safe, and comfortable for you and your guests.