Total Alkalinity (TA) is a fundamental measurement in pool chemistry that must be understood before adjusting other chemical levels. Although often confused with pH, TA and pH are distinct measurements. TA acts as the chemical foundation of the pool water, offering stability that directly influences how all other chemicals behave. Achieving the correct TA level is the first step in water balance, setting the stage for effective pH management.
Understanding Total Alkalinity and Its Importance
Total Alkalinity measures the concentration of alkaline substances dissolved in the water, primarily bicarbonates, carbonates, and hydroxides, expressed in parts per million (ppm). These alkaline compounds act as a buffer solution, resisting sudden changes in the water’s pH level. The ideal range for Total Alkalinity in a residential pool is between 80 and 120 ppm.
Maintaining this range prevents “pH bounce,” where the pH level fluctuates rapidly due to factors like rain, swimmer load, or sanitizers. Low TA indicates weak buffer capacity, causing the pH to swing wildly. Conversely, high TA can “lock” the pH at an elevated level. Regular testing using accurate test strips or a liquid test kit is necessary, as TA determines the stability of the entire water system.
The Interplay Between Total Alkalinity and pH
TA and pH are chemically linked, but they measure different things; TA is concentration, while pH is intensity (acidity or basicity). The buffering capacity of TA allows the pH to remain steady, keeping the water within the ideal swimming range of 7.4 to 7.6. If TA is too low, the water loses its buffering ability, leading to pH instability that can cause eye and skin irritation.
Low TA also increases the risk of corrosion on metal equipment and etching on plaster surfaces, as the water becomes more acidic. High Total Alkalinity makes it difficult to adjust the pH down, a condition often called “pH lock.” This elevated buffering capacity can lead to cloudiness and the formation of calcium scale deposits on pool walls and equipment, reducing circulation and filter efficiency. Because of this interdependence, all chemical adjustments should begin with correcting the TA level first, establishing a stable foundation.
Step-by-Step Guide to Raising Total Alkalinity
If testing reveals Total Alkalinity below 80 ppm, the standard method for raising it involves adding sodium bicarbonate, commonly known as baking soda. Pool alkalinity increaser products are primarily composed of this chemical, which boosts the concentration of alkaline materials. The general dosage guideline is that 1.5 pounds of sodium bicarbonate per 10,000 gallons of water will raise the TA by approximately 10 ppm.
First, calculate the pool’s volume and the needed increase, then measure the correct quantity of sodium bicarbonate. Sprinkle the powder directly across the pool surface, avoiding the skimmer, while the circulation pump is running for even distribution. It is better to add a conservative amount initially, perhaps half or three-quarters of the calculated dose, to prevent overshooting the target. After the chemical has circulated for six to twelve hours, retest the water to determine if a second application is necessary.
Step-by-Step Guide to Lowering Total Alkalinity
To reduce high Total Alkalinity (above 120 ppm), an acid must be introduced into the water. The two common chemicals used are Muriatic Acid (hydrochloric acid) or Sodium Bisulfate (dry acid). Lowering TA requires careful attention to safety protocols due to the corrosive nature of the chemicals. Always wear personal protective equipment (PPE), including gloves and eye protection, and ensure the area is well-ventilated when handling liquid acid.
To maximize the acid’s effect on TA, turn the pool pump off to stop water circulation. Pour the acid slowly into the deepest part of the pool. This technique allows the acid to stay concentrated, reducing the pH locally and targeting the alkalinity. After adding the acid, turn the pump on after about an hour to circulate the treated water. If the resulting pH is too low, the water can be aerated by running water features or pointing return jets upward, which naturally raises the pH without significantly affecting the TA.