Baking soda, also known as sodium bicarbonate, is a common household ingredient that has many uses besides baking. One of them is to raise the alkalinity of pool water, which can help prevent corrosion and scaling of pool equipment and surfaces. But how does baking soda work as an alkalinity increaser, and how much do you need to use? Here are some answers to these questions.
What is Alkalinity and Why is it Important?
Alkalinity is a measure of how well water can resist changes in pH, which is a measure of acidity or basicity. The pH scale ranges from 0 to 14, with 7 being neutral, lower values being acidic, and higher values being basic. Pure water has a pH of 7, but pool water can be affected by various factors such as rain, chlorine, organic matter, and bather load. These factors can lower or raise the pH of pool water, which can cause problems such as eye and skin irritation, chlorine inefficiency, metal staining, and algae growth.
To prevent these problems, pool water needs to have a stable pH level between 7.4 and 7.6, which is slightly basic and comfortable for swimmers. Alkalinity acts as a buffer that helps maintain this pH level by neutralizing acids or bases that are added to the water. The ideal alkalinity level for pool water is between 100 and 150 parts per million (ppm).
How Does Baking Soda Raise pH and Alkalinity?
Baking soda is a chemical compound with the formula NaHCO3. It is a salt composed of a sodium cation (Na+) and a bicarbonate anion (HCO3-). Baking soda is a weak base that can react with acids to form carbon dioxide, water, and salt. For example, when baking soda reacts with hydrochloric acid (HCl), it produces sodium chloride (NaCl), carbon dioxide (CO2), and water (H2O):
NaHCO3 + HCl -> NaCl + CO2 + H2O
When baking soda is added to pool water, it dissolves and releases bicarbonate ions into the water. These ions can combine with hydrogen ions (H+) from acids to form carbonic acid (H2CO3), which then breaks down into carbon dioxide and water:
HCO3- + H+ -> H2CO3 -> CO2 + H2O
By removing hydrogen ions from the water, baking soda reduces the acidity of the water and raises its pH. It also increases the concentration of bicarbonate ions in the water, which increases its alkalinity.
How Much Baking Soda Do You Need to Use?
The amount of baking soda you need to use depends on the size of your pool and the current alkalinity level of your pool water. You can test your pool water using a test kit or test strips to measure the alkalinity level. If it is below 100 ppm, you need to add baking soda to raise it. If it is above 150 ppm, you need to lower it using an acid such as muriatic acid or sodium bisulfate.
As a rule of thumb, you can use 1.5 pounds (680 grams) of baking soda per 10,000 gallons (37,854 liters) of pool water to raise the alkalinity by about 10 ppm. You can use this chart to find out how much baking soda you need for your pool size and desired alkalinity increase.
However, you should not add all the baking soda at once, as this can cause a sudden spike in pH that can damage your pool equipment and surfaces. Instead, you should add it gradually in small amounts over several days until you reach the desired alkalinity level. You should also test your pool water daily to monitor the changes in alkalinity and pH.
To add baking soda to your pool, you should first dissolve it in a bucket of warm water and then pour it into the pool near the return jet or skimmer. This will help distribute it evenly throughout the pool. You should also run your pool pump for at least six hours after adding baking soda to circulate the water.
Conclusion
Baking soda is an effective and inexpensive way to raise the alkalinity of your pool water. It works by releasing bicarbonate ions that buffer the pH and neutralize acids in the water. However, you should use it carefully and follow the instructions on how much to use and how to apply it. You should also test your pool water regularly to keep it balanced and safe for swimming.