Sodium bicarbonate, commonly known as baking soda, is a common chemical used in swimming pool maintenance. Its primary function is to adjust and stabilize the water chemistry, specifically by targeting the Total Alkalinity (TA) level. Many commercial “alkalinity increaser” products use sodium bicarbonate as their main active ingredient, making bulk baking soda a practical alternative for pool owners. Understanding how to correctly apply this substance is key to maintaining a balanced swimming environment.
The Primary Function of Baking Soda in Pool Water
The use of baking soda in pool care focuses on increasing the Total Alkalinity (TA) of the water. Total Alkalinity is the measure of dissolved alkaline substances, like bicarbonates, in the pool water, and it acts as a buffer against fluctuations in the pH level. This buffering capacity prevents the pH from swinging wildly between acidic and basic conditions, a phenomenon known as “pH bounce.”
If the TA level falls below 80 ppm, the water loses its ability to resist pH changes, leading to an unstable chemical environment. Low alkalinity causes the pH to become erratic and often makes the water acidic, which can corrode metal equipment like ladders and heaters, and damage the pool’s plaster or vinyl liner. The ideal range for Total Alkalinity is 80 ppm to 120 ppm, ensuring the pH remains stable within its optimal range of 7.4 to 7.6.
Baking soda works by dissolving in the water and releasing bicarbonate ions, which are the main components of alkalinity. While sodium bicarbonate has a naturally high pH of about 8.3, its primary and most significant effect is on the TA, with only a gentle, slight increase in the overall pH level. This makes it the preferred chemical for raising alkalinity without causing a sudden, large spike in pH that can lead to other problems like cloudy water or scale formation.
Calculating the Right Amount for Your Pool
Determining the exact amount of baking soda to add requires three pieces of information: the pool’s volume, the current Total Alkalinity reading, and the target increase needed. You must accurately know the number of gallons your pool holds, which can be calculated using its dimensions and shape. A reliable test kit is necessary to measure the current TA level in parts per million (ppm).
The standard rule of thumb for dosage is that 1.5 pounds of baking soda per 10,000 gallons of water will raise the Total Alkalinity by approximately 10 ppm. This formula allows for precise adjustment based on the difference between the current TA and the desired target level. For instance, if your pool is 15,000 gallons and the TA is 60 ppm, you will want to reach a minimum of 90 ppm, requiring a 30 ppm increase.
To calculate the total amount needed, first determine the total pounds required to raise 10,000 gallons by the target amount. Since a 30 ppm increase is needed, which is three times the 10 ppm standard, the base requirement is 4.5 pounds (1.5 lbs x 3). Because your pool is 15,000 gallons (1.5 times the 10,000-gallon standard), you multiply the base requirement by 1.5, resulting in 6.75 pounds of baking soda needed for the adjustment. Calculate the dose based on the needed increase in TA to avoid overshooting the ideal range.
Step-by-Step Application and Follow-Up
After calculation, the application process must ensure even dispersion and effective results. Keeping the circulation system running helps the powder dissolve and distribute more quickly throughout the water. The baking soda should be broadcast slowly and evenly across the surface of the pool, avoiding dumping it all in one spot, which can cause temporary cloudiness on the bottom.
Optionally, you can pre-dissolve the measured amount of baking soda in a large bucket of water before pouring the solution into the pool, which aids in faster mixing. After application, the pool’s pump and filter should circulate the water for a minimum of six to eight hours to fully distribute the sodium bicarbonate and allow it to react.
The final step is the follow-up retest of the water chemistry. Approximately 24 hours after adding the baking soda, retest both the Total Alkalinity and the pH levels using a reliable test kit. If the TA is still below the minimum target of 80 ppm, repeat the process with a new, smaller calculated dose. Make corrections slowly and in smaller increments, as adding too much at once can cause the TA to swing too high.