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What Temperature Should Water Be To Prevent Legionella?

Legionella is a bacterium that survives in water. It can thrive in natural or artificially build hot and cold water systems if they provide a favorable temperature for its growth. It causes Legionnaires’ disease, a severe type of pneumonia that leads to inflammation of lungs. It is transmitted through drinking water, inhaled water droplets, and contaminated soil. Legionnaires’ disease represents itself with mild fever to severe pneumonia. If it is left untreated or not managed properly, it may lead to death due to progressive pneumonia, septic shock, respiratory failure or multi-organ failure.

What Temperature Should Water Be To Prevent Legionella?

Legionella pneumophila thrives in water. It 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.

Legionella is an aerobic bacterium that is found in the aquatic environment. It was first found in 1976 in American Legion convention in Philadelphia. It was the cause of an outbreak of severe pneumonia in the convention center.

Legionella lives in both natural and artificially made water systems. 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.

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. Imaging scans can be performed in severe cases to detect the extent of damage to kidneys and lungs.

Legionnaires’ disease 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 and ventilation.

Thus, the temperature of indoor or outdoor artificially made water systems should be maintained under 20 degrees Celsius or above 60 degree Celsius. They should be cleaned at regular intervals. Stagnant water or water storage tanks should be vacant and cleaned regularly to prevent diseases caused by Legionella.


Legionella is waterborne bacteria that can cause serious health illness like Legionnaires’ disease. Legionella cannot survive in temperature below 20 degrees and above 60 degree Celsius. So, prevention of illness by legionella can be achieved by maintaining the temperature in the range 0-20 degrees or above 60 degrees.


  1. Centers for Disease Control and Prevention (CDC). “Legionella (Legionnaires’ Disease and Pontiac Fever).” https://www.cdc.gov/legionella/index.html
  2. European Centre for Disease Prevention and Control (ECDC). “Legionnaires’ disease.” https://www.ecdc.europa.eu/en/legionnaires-disease

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Team PainAssist
Team PainAssist
Written, Edited or Reviewed By: Team PainAssist, Pain Assist Inc. This article does not provide medical advice. See disclaimer
Last Modified On:August 4, 2023

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