One of the primary factors in the Bicarb Start process is maintaining the pool water pH at or below 8.3 as the pool fills. This ensures that calcium hydroxide in the pool’s surface plaster paste is converted to calcium carbonate without forming plaster “dust.”
Although the sodium bicarbonate (bicarb or baking soda) drives the pH of the fill water toward 8.3 and buffers the pH against moving away from that point, if the tap water is above that level to begin with, or if some other variables are in play, the barrel water may sometimes exceed 8.3 and some dusting may occur.
When we perform bicarb starts, we monitor the pH to make sure it stays below 8.3. Unfortunately, phenol red pH reagent maxes out its color-changing on the upper end around 8.3, so the purplish color at 8.3 is very difficult if not impossible to distinguish from the color of an 8.5, 9, or even higher reading.
There are several ways to get around this limitation of phenol red. One is to use a pH meter instead. This enables the service tech to see exactly if the pH is too high, and even by how much. The downside is both the expense and also the potential fragility of such equipment at poolside.
Another method, that we employ, is the reagent phenolphthalein. This is a reagent that, when added to water below 8.3 remains colorless. If the pH of the solution is above 8.3 the reagent turns pink. A few drops from a bottle of phenolphthalein into a bicarb barrel or into the water in the bowl of the pool will quickly reveal if there is an adjustment needed or not… colorless is good, and pink means add acid.
When we need to add acid during a bicarb start there are several options. One is to add a capful at a time to the water in the bowl of the pool until additional drops of phenolphthalein remain colorless. Then we add the rest of the gallon to the bicarb barrel. Another option is the introduction of boric acid, which lowers the pH as well as introducing the buffering and other benefits that borate provides long term.