A Deeper Look at Alkalinity

Of all water balance parameters, “alkalinity” may be the least understood. Alkalinity is what helps maintain a proper pH (from 7.2 to 7.8), and buffers, or resists wild pH fluctuations when sanitizers or other chemicals are added to pool water.

Sanitizers, when added to water, in addition to providing chlorine, also have an acidic (acid or low pH) or an alkaline (basic or high pH) effect on the water. It is the alkalinity (primarily in its bicarbonate form) that reacts with and “absorbs” the pH-altering effect of the sanitizer. This process “buffers” the pH, but may also either add to or lower the total amount of alkalinity in the water. Adding other types of chemicals also may have an effect on pH, and those effects are also “buffered” by the alkalinity.

The APSP has established that pool water should have a minimum of 60 ppm and a maximum of 180 ppm of total alkalinity. If the total alkalinity is below 60 ppm, there may not be enough alkalinity (buffering capacity) to resist a significant pH change if an acidic or basic chemical is added. In the case of adding an acid, the pH could drop below 7.0, making the water very corrosive to pool plaster, metal fixtures and equipment, as well as being very irritating to swimmers’ eyes. In the case of adding a high pH (alkaline) chemical, the pH could go excessively high (over 8.3), which increases the likelihood of calcium carbonate (scale) depositing onto the pool surface and equipment.

Source: Pool Genuis Network