How Much Chlorine Should Be in a Pool?

Residual Chlorine is the most common sanitizer used in swimming pools. It prevents the growth of microorganisms like bacteria and algae in the water. It is an efficient sanitizer at low concentrations, and when properly stabilized. Below a concentration of 1.0 ppm, chlorine is not very effective at killing microorganisms. Using more than 3.0 ppm does not improve the effectiveness of sanitization and comes at an increased cost ($). It is critically important to know that prolonged periods of elevated chlorine can damage the pool liner, causing premature fading or stiffness. Maintaining the proper free chlorine level in a swimming pool keeps water clean and safe.

NOTE: How often the chlorine in a pool needs to be replenished is called the chlorine demand. A higher chlorine demand does not mean your chlorine levels should be kept higher than 3 ppm – it means it needs to be topped up more often. See the next section for some things that can affect chlorine demand, and if you’re having trouble maintaining your levels between 1.0 and 3.0 ppm, consult your pool dealer.