In what units is chlorine residual typically measured?

Chlorine residual is most commonly measured in mg/L, which stands for milligrams per liter. This unit is widely used in water quality analysis as it effectively conveys the concentration of chlorine in water. Since chlorine is typically present in very small quantities in treated water, using milligrams per liter allows for precise measurement and monitoring of chlorine levels, essential for ensuring that the water is safe for consumption and meets regulatory standards.

While ppm also represents a concentration metric similar to mg/L—since 1 ppm is equivalent to 1 mg/L for water—mg/L is the preferred unit in the context of water quality testing. This is because measured values are often expressed in terms of mass per volume, making mg/L a more straightforward and useful metric for the concentrations typically found in water sources.

The other units listed are less suited for measuring chlorine residual in typical water quality assessments. Grams per liter would suggest much higher concentrations than what is generally encountered in drinking water, while milliliters per liter is not appropriate in this context as it measures volume rather than mass. Therefore, mg/L is the standard unit used for reporting chlorine residual in water quality analysis.