Chlorine levels in pool water

Swimming pool and pool house image by Jim Mills from

Chlorine is a common chemical used in swimming pools to sanitise the water and keep them germ- and algae-free. However, chlorine can be harmful in high doses and even in low doses if regularly exposed.

Therefore, it is important to maintain proper chlorine levels in your pool water to keep your swimming pool sparkling, clean and safe.

Chlorine Levels

Chlorine filters or feeders should be installed in your swimming pool to automatically adjust chlorine levels to the correct amount. These feeders slowly release chlorine into the water throughout the day to maintain a consistent level. The recommended chlorine level for a typical swimming pool is 1.0 to 2.0 ppm (parts per million).

A high level of chlorine in a pool can be dangerous. See below for symptoms of chlorine overexposure.

PH Levels

It is also essential to maintain the correct pH level in your swimming pool, as high or low pH levels can render chlorine ineffective. Also, symptoms often associated with high chlorine levels such as red eye are actually symptoms of low pH levels. The recommended pH level for a typical swimming pool is 7.2 to 7.8.


Swimming pools should be tested for chlorine and pH concentrations at least twice a week. There are several chlorine testers available at pool supply stores, but it is worth it to shell out a few extra dollars to buy a comprehensive chlorine tester for a precise reading. DPD chlorine testers work well, as these measure all forms of chlorine as well as pH levels.

A DPD chlorine tester will turn red when exposed to chlorinated water. The darker it turns, the more chlorine is present. However, a very high chlorine concentration can bleach out a DPD tester, making it appear clear and chlorine-free. Be sure to dilute your chlorine sample with regular water if the tester shows a clear reading but the presence of chlorine is suspected.

Chlorine Over-Exposure

Chlorine can produce derivatives called nitrogen trichloride and chloroform. These, and other chlorine derivatives, are produced when chlorine comes into contact with organic compounds such as sweat or urine. Studies have linked these chemicals to asthma and allergies in swimmers. In fact, one famous study showed regular exposure to this chlorine chemical can cause lung damage to the extent seen in heavy smokers. Symptoms of chlorine allergies include irritated skin, hay fever, itchy eyes, sore throat and respiratory problems. Keep chlorine levels as low as possible, while retaining a clean, clear swimming pool, to prevent overexposure to this chemical.


There are several natural alternatives to chlorine, which can be effective in keeping pools clean, sanitary and safe. Salt water is a natural alternative that can also make pool maintenance much simpler. Ionisation or oxidation are also methods used to kill contaminants in water, as well as purifying plants. These may be supplemented by low levels of chlorine for maximum effectiveness.