Can Legionella Survive in Chlorinated Water?

Legionella is an aerobic bacterium that survives in the aquatic environment in favorable temperatures. It lives in both natural and artificially made water systems. It grows and multiplies in the water systems that have temperatures in between 20-45 degree Celsius. It can cause serious illness like Legionnaires’ disease in individuals who have low immunity. It spreads through drinking water, inhaled water droplets, and contaminated soil. Water systems should be treated regularly to inhibit the growth and multiplication of the bacteria.

Can Legionella Survive in Chlorinated Water?

Can Legionella Survive in Chlorinated Water?

Legionella is a species of bacteria that is found in water. It was first detected in 1976 in American Legion convention in Philadelphia. It was the cause of an outbreak of severe pneumonia in the convention center.

Legionella grows and multiplies in the water systems that have temperatures in between 20-45 degree Celsius. It remains inactive in temperatures under 20 degrees Celsius and dies above 60 degree Celsius.

It lives in water sources such as ponds, river, swimming pools, hot springs, usually in low density and cannot cause infection. It can grow in indoor water systems like hot water tubes, mist sprayers or air conditioners. Sometimes, it can multiply in the artificial water system of home and industry. It can be found in cooling towers of air conditioning that use water for cooling in the air condensing systems, hot and cold water systems used in public or private buildings, and whirlpool spas. Whirlpools and spas provide an ideal atmosphere for the bacteria to grow as they are rich in nutrients for its growth.

Legionella is also found in potting soil or moist soil. Stagnant water is found in dead ends of pipes or in large water tanks. It can provide nutrients and exact favorable environment for the bacteria to grow and multiply.

Infection by Legionella occurs when an individual drinks contaminated water, inhales contaminated water droplets or aspires contaminated liquid accidentally or comes in contact with contaminated soil.

Contamination of water happens due to poor maintenance of swimming pools, hot tubs, water pipes, hot water heaters and other plumbing systems.

However, Legionella bacteria cannot survive in chlorinated water. But at some phases, it can develop resistance against chlorine. It can survive the water treatment in the cystic stage. In warm water, the cysts of Legionella can even survive the exposure of up to 50 ppm of chlorine.

Legionnaires’ disease is a serious ailment of lungs caused by Legionella bacteria. It is most commonly spread by inhalation of contaminated water droplets present in air formed due to water sprays, jets or mists or by aspiration of contaminated water or ice. Outbreaks of Legionnaires’ disease occur more commonly in summer season or in early autumn season. However, it can occur in any season in a year. Its outbreak is supported by the plumbing system of large buildings where legionella can grow, multiply and spread easily. Legionnaires’ disease can represent itself with mild febrile conditions to severe pneumonia leading to lung failure.

The Symptoms Of Legionnaires’ Disease Are-

Legionnaires’ disease is diagnosed by the urine test and blood tests. It requires immediate diagnosis and treatment as it may complicate into conditions like progressive pneumonia, respiratory failure, septic shock, kidney failure or even death. It can be treated with antibiotics.


Legionella thrives in the aquatic environment and can infect your lungs when you drink contaminated water, or inhale an aerosol containing them or come in contact with contaminated soil. Its infection can be prevented to a great extent by regular disinfection and cleaning. It cannot live in the chlorinated water. Its amoebic cyst can survive even the water treatment by chlorine.

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