Meeting a chlorine demand
Chlorine demand is a problem faced by many pools that use the chemical as the sanitizer of choice. A chlorine demand is present when the pool shows the consistent inability to establish a sanitizer residual. This occurs when there are too many contaminants consuming the chlorine and not enough sanitizer in the water to oxidize these pollutants. Pools in a demand have no sanitizer available for bather protection. The chlorine generator cell often cannot make chlorine quickly enough to provide the amount needed to overcome the demand. If the need is large, an additional source of chlorine is required to break the demand and re-establish the sanitizer level.
There are times when the pool may not be in a chlorine demand, but it still may not be able to maintain a free chlorine residual. Common causes for this include:
Not running the cell generator long enough
As the electrolytic cell only generates chlorine while the pump is running, ensuring the equipment operates for the required amount of time is critical.
An undersized cell
Using a cell that is too small for the pool can also result in low chlorine residual. An undersized cell may not be able to produce enough sanitizer to maintain 1 to 4 parts per million (ppm) chlorine residual, even with ample pump run time and setting the cell for maximum output.
Scale accumulation on the cell plates
Scale deposits can also impact how well an electrolytic cell produces chlorine. Buildups are more likely to occur as the pH of a saltwater pool increases. Once the scale accumulation is substantial, it will reduce the ability of the cell plates to pass electricity through them. Electricity, generated through electrolysis, is the key to chlorine production. The higher the scale buildup, the less chlorine is produced.
There are two types of calcium scale formations: calcium carbonate and calcium phosphate. Each accumulation is influenced by different factors. Calcium carbonate is the most common type of scale found within any pool environment and makes up the majority of buildups found on chlorine generator cell plates. These scale formations are influenced by three main factors: water temperature, pH, and concentration.
On the other hand, several water-balance parameters lead to the formation of calcium phosphate. That said, this scale buildup is not driven by high pH. However, higher concentrations of both calcium and phosphate in the pool will cause increased risk of scale formation.
It is imperative to use a scale inhibitor product to help prevent buildups in chlorine generator pools. In addition, some manufacturers warn against high phosphate levels to prevent the small amount of calcium phosphate scale that may form in the chlorine generator. Adding a phosphate remover into the pool maintenance routine can help reduce problem-causing phosphate-based scale and improve cell efficiency.
