It is more difficult to control pH and total alkalinity in spas than in pools, because high water temperature and aeration ( air coming into the water through air blowers and jets) speed up the loss of carbon dioxide to the atmosphere; in the form of dissolved carbonic acid, carbon dioxide lowers the pH. As water temperatures rise, dissolved gases like carbonic acid become less soluble and “gas off”. Air Moving through the water from blowers and jets speeds up this effect, causing pH to rise.
Also, without carbonic acid, the bicarbonate buffer cannot control the pH and keep it from rising. The pH of a “balanced” spa can increase from 7.4 to 8.3 in as little as 40 minutes. In a spa “balanced” means pH is 7.4, total alkalinity is 120 ppm, and chlorine level are 3 ppm. If you add a pH decreaser at this point to your spa, the pH decreases only temporarily. If you add more pH decreaser than needed for pH control, you may over-reduce the total alkalinity and lose the water’s buffering capacity. More additions could then cause the pH to decrease quickly.
The rise in pH may cause cloudy water due to the formation of calcium carbonate. High pH and temperature cause bicarbonates to convert to carbonates by losing CO2 and water. The carbonates then unite with calcium in the water to form scale, which can cloud spa water, clog spa heaters, and roughen and discolor you spas surface.
This all may sound scary and even a little difficult to understand, but do not worry. Once you have your total alkalinity levels established, and have your pH in range, it is a matter of checking your spa water daily and adding the prescribed amount of spa product to maintain the aforementioned “balanced” levels.





