Free Chlorine

Chlorine in water may be present in two forms, free and combined: Free chlorine does the hard work of killing bacteria and oxidising contaminants. When you add chlorine to water, you are actually adding free chlorine. When the free chlorine combines with contaminants, it becomes combined chlorine, or chloramines. In water, this form of chlorine has very little sanitising ability and no oxidising ability. Total chlorine is the sum of both – combined chlorine and free chlorine. Levels of chlorine should be kept as low as possible whilst still ensuring the quality of the water.

Testing for free as well as total chlorine is important, to ensure that the correct amount of sanitiser is being added to water.

Choose the free Chlorine test, depending on the range you want to cover, ie. the level of chlorine added at the water treatments works is usually up to 1 ppm (mg/l). Your local swimming pool will normally have a concentration between 1.5 and 5 ppm (mg/l).