Key Facts

According to the CDC, Legionella bacteria has a broad range of potential growth. “Legionella bacteria exist in the biofilm on the inside of pipes. Legionella grows rapidly between 77°F and 108°F.” Although it may seem feasible to raise the water temperature to 140°F, this leaves the water in the scald temperature range.” (22)

The International Plumbing Code Section 424.4: states, “Shower and tub/shower combination valves shall be balanced pressure, thermostatic, or a combination of balanced pressure/thermostatic valves that conform to the requirements of ASSE 1016 or CSA B125. Valves shall be equipped with a means to limit the maximum setting of the valve to 120°F, which shall be field adjustable in accordance with the manufacturers’ instructions.” (22)

“When a residential water heater is used, the codes do not limit the temperature to 140F, so it is not uncommon to find water at 160 degrees F.” This temperature will scald a child with third-degree burns in only .25 seconds. (22)

How common is Legionella bacteria in my hot water tank?

“In Quebec, a study of 211 homes (178 electric water heaters, 33 oil or gas water heaters) found Legionella contamination in 40% of electric water heaters. No water heaters using fossil fuels were contaminated. The authors concluded that, because of design variables, use of an electric water heater was the most significant factor leading to Legionella contamination in hot water in the home.” (28)

What are the affects?

Occurrences of Legionellosis have happened while people have been exposed to a infected water source and inhaled contaminated water: cooling towers, whirlpools, bathtubs, showers or even at a steamy faucet. Legionella has been shown to most greatly affect people whose immune system is low. For example in a hospital setting, patients that are most susceptible to Legionella infection include: cancer patients who are in radiation or chemotherapy treatments, organ-transplants, HIV, elderly and surgical patients. Severe Legionnaires’ disease has an overall mortality rate of 10% to 30% (1-3), and 30% to 50% of patients require admission to an intensive care unit (1-4) Additional source: Center for Disease Control and Prevention

(22)Ackroyd, R. (2001). 25 years and 125,000 scalds. Retrieved July 28, 2005, from Innovative Valves, Faucets and Plumbing Specialties Web site: http://www.pmengineer.com/CDA.

(23)Falco V, Fernandez de Silva, Alegre J, Ferrer A, Martinez Vasguez JM. Legionella pneumophila: a cause of severe community-acquired pneumonia. Chest 1991;100:1007–11.

(24)Marston BJ, Lipman HB, Breiman RF. Surveillance for Legionnaires’ disease: risk factors for morbidity and mortality. Arch Intern Med 1994;154:2417–22.

(25)el-Ebiary M, Sarmiento X, Torres A, Nogue S, Mesalles E, Bodi M, et al. Prognostic factors of severe Legionella pneumonia requiring admission to ICU. Am J Respir Crit Care Med 1997;156:1467–72.

(26)Tobin JO, Beare J, Dunnill MS, Fisher-Hoch S, French M, Mitchell RG, et al. Legionnaires’ disease in a transplant unit: isolation of the causative agent from shower baths. Lancet 1980;2:118–21.

(27)Ackroyd, R. (2001). 25 years and 125,000 scalds. Retrieved July 28, 2005, from Innovative Valves, Faucets and Plumbing Specialties Web site: http://www.pmengineer.com/CDA.

(28)Levesque M.D., B. (2004). Residential water heater temperature: 49 or 60 degrees celcius?. The Canadian Journal of Infectious Diseases & Medical Microbiology, 15. Retrieved Jul 21, 2005, from http://www.pulsus.com/Infdis/15_01/leve_ed.htm.