Chlorine in Pool Water and Nearby Plants

Today there are many homes that have swimming pools as well as municipal pools in the cities. Many people ask, “Will the chlorine from the pool that gets on the plants around the pool harm them?”

It is important to remember that chlorine does not occur naturally in nature, chloride (Cl^-) is readily soluble, highly mobile and easily taken up by plants. Chloride is the element that is found in fertilizer materials.

Chlorine (Cl₂) is a corrosive, poisonous gas used to make bleaching agents and disinfectants. The form of chlorine most often added to pool water is solid calcium hypochlorite which forms hypochlorous acid (HOCl) when place in water. Sodium hypochlorite is the active ingredient of common household bleach. Commercial liquid chlorine (compressed chlorine gas) is used as a water treatment to kill bacteria. Hypochlorous acid is the effective agent that controls algae growths in pools.

According to Clemson University, “There should be no effect of pool water splashed on nearby plants from normal pool use. Larger plants (and animals) can tolerate the concentrations that are recommended for pool water.”

Dr. Alison Osinski (Aquatic Consulting Services, San Diego, CA) suggests, “If the pool or spa water has a high chlorine content, uncover it and allow the chlorine to dissipate before using the water for irrigating the landscape. Or, chemically remove the chlorine by adding solium thiosulfate of sodium sulfite to the water.”

Chloride (Cl^-) is the ionic form of chlorine found in nature. It has a negative charge and is often associated with sodium (common table salt) or other positively charged ions like potassium. It is non-toxic and readily absorbed and used by plants.

Compare the concentrations of chloride and chlorine in water. Sea water, which contains high levels of bacterial life, contains chloride levels of around 20,000 ppm. Water treatment plants aim for chlorine levels of 1.7 ppm to disinfect water.