Algae are microscopic organisms that can grow in water and cause various problems for pool owners. They can make the water cloudy, green, or slimy, and reduce the effectiveness of chlorine. Algae can also affect the pH and alkalinity of the pool water, which are important parameters for maintaining water quality and balance.
What is Alkalinity and Why is it Important?
Alkalinity is a measure of how well the water can resist changes in pH. pH is a measure of how acidic or basic the water is. The ideal pH range for pool water is 7.2 to 7.8, which is slightly basic. If the pH is too low (acidic), it can cause corrosion of metal parts, irritation of skin and eyes, and chlorine loss. If the pH is too high (basic), it can cause scaling of pipes and equipment, cloudy water, and reduced chlorine effectiveness.
Alkalinity acts as a buffer that helps keep the pH stable. It does this by neutralizing acids or bases that are added to the water. The ideal alkalinity range for pool water is 80 to 120 parts per million (ppm). If the alkalinity is too low, the pH can fluctuate easily and cause damage to the pool and discomfort to the swimmers. If the alkalinity is too high, the pH can become too high and cause scaling and cloudy water.
How Does Algae Affect Alkalinity?
Algae can affect alkalinity in two ways: by consuming carbon dioxide and by releasing organic acids.
- Carbon dioxide is one of the forms of alkalinity in water. It reacts with water to form carbonic acid, which lowers the pH. Algae use carbon dioxide for photosynthesis, which is the process of converting light energy into chemical energy. When algae consume carbon dioxide, they reduce the amount of carbonic acid in the water, which raises the pH and lowers the alkalinity.
- Organic acids are substances that release hydrogen ions when dissolved in water. They lower the pH and increase the acidity of the water. Algae produce organic acids as a by-product of their metabolism. When algae die, they decompose and release more organic acids into the water. These organic acids lower the pH and reduce the alkalinity of the water.
How Does Algaecide Affect Alkalinity?
Algaecide is a chemical substance that is used to kill or prevent algae growth in pools. There are different types of algaecides available, such as copper-based, quaternary ammonium, polyquat, or peroxide-based algaecides. Each type has a different mechanism of action and a different effect on alkalinity.
- Copper-based algaecides work by disrupting the cell membranes and enzymes of algae. They are effective against many types of algae, but they can also stain pool surfaces and equipment if used excessively or improperly. Copper-based algaecides do not directly affect alkalinity, but they can lower it indirectly by killing algae and reducing carbon dioxide consumption.
- Quaternary ammonium algaecides work by interfering with the cell membranes and respiration of algae. They are effective against green algae, but they can also cause foaming and reduce chlorine effectiveness if used excessively or improperly. Quaternary ammonium algaecides do not directly affect alkalinity, but they can lower it indirectly by killing algae and reducing carbon dioxide consumption.
- Polyquat algaecides work by forming a protective layer around algae cells and preventing them from reproducing. They are effective against all types of algae, but they can also be expensive and degrade over time if exposed to sunlight or chlorine. Polyquat algaecides do not directly affect alkalinity, but they can lower it indirectly by killing algae and reducing carbon dioxide consumption.
- Peroxide-based algaecides work by oxidizing algae cells and breaking them down into harmless substances. They are effective against all types of algae, but they can also cause temporary cloudiness and reduce chlorine levels if used excessively or improperly. Peroxide-based algaecides do not directly affect alkalinity, but they can lower it indirectly by killing algae and releasing organic acids into the water.
How to Maintain Alkalinity After Using Algaecide?
As you can see, algaecide can lower alkalinity in pools by killing algae and affecting the chemical balance of the water. Therefore, it is important to monitor and adjust alkalinity after using algaecide to prevent pH fluctuations and other problems.
To maintain alkalinity after using algaecide, you should follow these steps:
- Test your pool water regularly using a reliable test kit or strips. You should test for pH, chlorine, alkalinity, calcium hardness, cyanuric acid, and metals at least once a week.
- If your alkalinity is below 80 ppm, you should raise it by adding baking soda (sodium bicarbonate) to the pool. Baking soda is a base that increases the alkalinity and pH of the water. You should add about 1.5 pounds of baking soda per 10,000 gallons of water to raise the alkalinity by 10 ppm. You should add the baking soda slowly and evenly to the pool, preferably near the return jets or skimmer. You should wait at least 4 hours before retesting and adjusting the alkalinity again.
- If your alkalinity is above 120 ppm, you should lower it by adding muriatic acid (hydrochloric acid) or dry acid (sodium bisulfate) to the pool. Muriatic acid and dry acid are acids that decrease the alkalinity and pH of the water. You should add about 1.6 fluid ounces of muriatic acid or 2.4 ounces of dry acid per 10,000 gallons of water to lower the alkalinity by 10 ppm. You should add the acid slowly and carefully to the pool, preferably in a bucket of water and away from metal parts or pool surfaces. You should wait at least 4 hours before retesting and adjusting the alkalinity again.
- If your pH is out of range, you should adjust it after adjusting the alkalinity. You should use a pH increaser (sodium carbonate) to raise the pH or a pH decreaser (sodium bisulfate) to lower the pH. You should follow the instructions on the product label and wait at least 4 hours before retesting and adjusting the pH again.
Algaecide is a useful tool for controlling algae in pools, but it can also lower alkalinity by affecting the chemical balance of the water. Alkalinity is important for maintaining pH stability and water quality in pools. Therefore, you should monitor and adjust alkalinity after using algaecide to prevent pH fluctuations and other problems.