Chlorine is a chemical that is used to sanitize pool water and kill harmful bacteria and algae. But does chlorine also affect the alkalinity of the pool water? And if so, how can you balance the chlorine and alkalinity levels to keep your pool safe and comfortable?
What is Alkalinity and Why is it Important?
Alkalinity, or total alkalinity, measures your water’s ability to resist changes in pH, and it’s responsible for keeping your pH level stable. PH is a measure of how acidic or alkaline the water is, and it affects the effectiveness of chlorine and the comfort of swimmers. The ideal pH level for your pool water is slightly basic at somewhere between 7.2 to 7.6. This is where chlorine works best without making the water too harsh on your skin, hair, and eyes.
Keeping your pH level within this range is extremely difficult without total alkalinity keeping guard, as it provides a buffer to counteract small changes in the water chemistry. Without it, your pH could fall too low, causing the water to become corrosive to your pool surfaces and equipment, or drift too high, leading to calcium scaling.
The ideal total alkalinity level for your pool water depends on the type of pool you have. For vinyl pools, the recommended range is 100 to 150 parts per million (ppm), while for gunite pools, the range is 80 to 120 ppm. If your total alkalinity is too low, your pH will be unstable and prone to fluctuations. If your total alkalinity is too high, your pH will be resistant to adjustment and tend to rise.
How Does Chlorine Affect Alkalinity?
Chlorine can affect alkalinity in different ways depending on the type of chlorine you use and how you add it to your pool. There are two main types of chlorine: stabilized and unstabilized. Stabilized chlorine contains cyanuric acid, which protects chlorine from being degraded by sunlight. Unstabilized chlorine does not contain cyanuric acid, but it may contain other chemicals that affect the pH and alkalinity of the water.
Stabilized chlorine products, such as chlorine tablets or granules, tend to lower the pH and raise the total alkalinity of the pool water over time. This is because cyanuric acid is an acidic substance that consumes hydroxides in the water, which are part of the total alkalinity. As a result, the pH drops, and the total alkalinity increases.
Unstabilized chlorine products, such as liquid chlorine or calcium hypochlorite, tend to raise the pH and lower the total alkalinity of the pool water over time. This is because these products contain hydroxides or carbonates that increase the pH and consume bicarbonates in the water, which are also part of the total alkalinity. As a result, the pH rises and the total alkalinity decreases.
The way you add chlorine to your pool can also affect how much it changes the pH and alkalinity. If you add chlorine directly to the pool water without diluting it first, you create a localized area of high concentration that can cause a sudden spike or drop in pH. This can damage your pool surfaces and equipment, as well as irritate your eyes and skin. To avoid this, you should always dilute chlorine in a bucket of water before adding it to your pool, preferably near a return jet to disperse it evenly.
How Do You Balance Chlorine and Alkalinity?
To balance chlorine and alkalinity in your pool, you need to test your water regularly using a reliable test kit or strips. You should aim to maintain a free chlorine level of 1.0 to 4.0 ppm, a pH level of 7.2 to 7.6, and a total alkalinity level of 80 to 120 ppm for gunite pools or 100 to 150 ppm for vinyl pools.
If your chlorine level is too low, you need to add more chlorine to your pool using either stabilized or unstabilized products depending on your cyanuric acid level. If your cyanuric acid level is below 30 ppm, you can use stabilized chlorine products. If your cyanuric acid level is above 50 ppm, you should use unstabilized chlorine products.
If your pH level is too low or too high, you need to adjust it using either a pH increaser or a pH decreaser product. A common pH increaser product is soda ash (sodium carbonate), which raises both pH and total alkalinity. A common pH decrease product is muriatic acid (hydrochloric acid), which lowers both pH and total alkalinity.
If your total alkalinity level is too low or too high, you need to adjust it using either an alkalinity increaser or an alkalinity decreaser product. A common alkalinity increaser product is baking soda (sodium bicarbonate), which raises both total alkalinity and pH. A common alkalinity decrease product is sodium bisulfate, which lowers both total alkalinity and pH.
When adjusting your pH and total alkalinity, you should always follow the manufacturer’s instructions and add the products slowly and in small amounts. You should also wait at least four hours before retesting your water and making further adjustments. This will allow the chemicals to circulate and mix well in the pool.
How Do You Maintain Chlorine and Alkalinity?
To maintain chlorine and alkalinity in your pool, you should follow a regular routine of testing, sanitizing, shocking, and balancing your water. You should also keep your pool clean and free of debris, algae, and organic contaminants that can affect your water chemistry.
You should test your water at least once a week using a test kit or strips. You should check your free chlorine, pH, total alkalinity, and cyanuric acid levels and make any necessary adjustments. You should also test your water after heavy rain, wind, or bather load, as these can alter your water balance.
You should sanitize your pool daily using either stabilized or unstabilized chlorine products depending on your cyanuric acid level. You should aim to maintain a free chlorine level of 1.0 to 4.0 ppm at all times. You should also use a chlorine stabilizer product if your cyanuric acid level is below 30 ppm to prevent chlorine loss due to sunlight.
You should shock your pool weekly or as needed using either a chlorine or a non-chlorine shock product. Shocking your pool means adding a large dose of sanitizer to oxidize and destroy any organic contaminants that can reduce the effectiveness of chlorine and cause cloudy water, algae growth, or unpleasant odors. You should shock your pool when your free chlorine level drops below 1.0 ppm, when your combined chlorine level exceeds 0.5 ppm, or when your water looks dull or cloudy.
You should balance your pool monthly or as needed using either a pH increaser or a pH decreaser product and either an alkalinity increaser or an alkalinity decreaser product. Balancing your pool means adjusting your pH and total alkalinity levels to keep them within the ideal range of 7.2 to 7.6 for pH and 80 to 120 ppm for gunite pools or 100 to 150 ppm for vinyl pools for total alkalinity. Balancing your pool will help prevent corrosion, scaling, staining, and other problems caused by unbalanced water.
The Bottom Line
Chlorine is essential for keeping your pool water clean and safe, but it can also affect the alkalinity of the water depending on the type of chlorine you use and how you add it to your pool. To keep your pool water balanced and comfortable, you need to test, sanitize, shock, and balance your water regularly using the appropriate products and methods. By doing so, you will enjoy a sparkling and healthy pool all season long.