If you own a pool, you probably know that maintaining the right water chemistry is essential for keeping it clean, safe, and comfortable. But do you know what pool alkalinity is and why it matters? In this article, we will explain what pool alkalinity is, how it affects your pool’s pH level, and how to test and adjust it.
What is Pool Alkalinity?
Pool alkalinity, also known as total alkalinity (TA), is the measure of how well your pool water can resist changes in pH. It is composed of various substances that act as buffers, such as carbonates, bicarbonates, hydroxides, and cyanurates. These buffers absorb acids and bases that are introduced to the water by various sources, such as rain, leaves, dirt, sweat, urine, and chemicals.
Why is Pool Alkalinity Important?
Pool alkalinity is important because it helps to keep your pool’s pH level stable. The pH level is the measure of how acidic or basic your pool water is, and it affects the effectiveness of chlorine, the comfort of swimmers, and the health of your pool surfaces and equipment. The ideal pH range for pools is between 7.2 and 7.8.
If your pool alkalinity is too low, your pool water will have little or no buffering capacity, which means that any small amount of acid or base can cause a large change in pH. This can result in:
- Chlorine becomes too strong and loses its sanitizing power quickly.
- Water becomes corrosive and damages your pool surfaces and equipment.
- Water becomes irritating to your eyes, skin, hair, and mucous membranes.
- The water becomes cloudy and prone to algae growth.
If your pool alkalinity is too high, your pool water will have too much buffering capacity, which means that it will be hard to adjust the pH level. This can result in:
- Chlorine becoming too weak and losing its sanitizing power.
- Water becoming basic and causing calcium scaling on your pool surfaces and equipment.
- Water becomes irritating to your eyes, skin, hair, and mucous membranes.
- The water becomes cloudy and prone to algae growth.
What is the Ideal Alkalinity Level?
The ideal alkalinity level for pools is between 80 and 120 parts per million (ppm). This range provides enough buffering capacity to prevent large pH swings while allowing easy pH adjustment when needed. However, some factors may affect the optimal alkalinity level for your pool, such as:
- The type of chlorine you use: If you use stabilized chlorine products, such as tablets or granules, they will add cyanuric acid to your water, which will increase your total alkalinity. In this case, you may need to lower your alkalinity level to avoid high pH problems.
- The type of pool surface you have: If you have a plaster or concrete pool surface, they will tend to raise your pH level over time due to their alkaline nature. In this case, you may need to lower your alkalinity level to avoid scaling problems.
- The hardness of your fill water: If you have hard water in your area, it will contain high levels of calcium and magnesium, which will increase your total alkalinity. In this case, you may need to lower your alkalinity level to avoid scaling problems.
How to Test Total Alkalinity?
To test your pool’s total alkalinity level, you will need a test kit or test strips that measure TA. You can find these at any pool supply store or online. Follow the instructions on the package to perform the test. Usually, you will need to fill a test tube with a sample of pool water and add a few drops of a reagent that changes color according to the TA level. Then compare the color with a chart provided by the manufacturer.
Alternatively, you can use a digital tester that gives you a numerical reading of the TA level. These are more accurate and convenient than manual testers but also more expensive.
How to Adjust Total Alkalinity?
If your pool’s total alkalinity level is out of range, you will need to adjust it by adding chemicals that either increase or decrease TA. These are:
- Sodium bicarbonate (baking soda): This is used to raise TA by adding bicarbonate ions to the water. It also raises the pH slightly, so you may need to lower it afterward with an acid. The amount of baking soda you need to add depends on the size of your pool and the current and desired TA levels. You can use an online calculator to determine the exact dosage.
- Sodium bisulfate (dry acid): This is used to lower TA by adding sulfate ions to the water. It also lowers pH significantly, so you may need to raise it afterward with a base. The amount of dry acid you need to add depends on the size of your pool and the current and desired TA levels. You can use an online calculator to determine the exact dosage.
When adding chemicals to adjust TA, follow these steps:
- Turn off your pool pump and heater.
- Pre-dissolve the chemical in a bucket of water and stir well.
- Pour the solution slowly and evenly around the perimeter of your pool.
- Wait at least 4 hours before turning on your pool pump and heater.
- Wait at least 24 hours before retesting your TA level and making further adjustments if needed.
How to Maintain Total Alkalinity?
To maintain your pool’s total alkalinity level within the ideal range, you should:
- Test your TA level at least once a week or more often if you notice changes in your water quality or clarity.
- Adjust your TA level as soon as possible if it is out of range using the chemicals and methods described above.
- Avoid adding too much or too little chlorine to your pool, as this can affect your TA level. Follow the manufacturer’s instructions on how to dose chlorine properly for your pool size and type.
- Avoid adding unnecessary chemicals to your pool, such as algaecides, clarifiers, or shock treatments, as they can affect your TA level. Only use them when needed and follow the manufacturer’s instructions on how to use them safely and effectively.
- Avoid adding too much or too little water to your pool, as this can affect your TA level. Check your water level regularly and fill or drain your pool as needed to keep it at the recommended level.
The Bottom Line
Pool alkalinity is an important factor that affects your pool’s pH level, which in turn affects the effectiveness of chlorine, the comfort of swimmers, and the health of your pool surfaces and equipment. By testing and adjusting your TA level regularly, you can keep your pool water balanced and prevent common problems such as corrosion, scaling, irritation, and algae growth.