Legionella in Homes

Today, most hospitalized patients have short hospital stays and are often sent home with serious medical conditions. An unfortunate consequence of this practice is an ever-expanding pool of individuals that may be susceptible to Legionella infection from exposure within their homes.

In 1987, SPL published the first report of community-acquired Legionnaires’ disease acquired from exposure within the home. Subsequent reports in 2004 showed that 6% to 32% of homes could be colonized with Legionella.

What is the risk for contracting Legionnaires’ disease from home water systems?

The risk remains low for healthy individuals. Our 1992 study of 218 American Legion members’ homes across six counties in Western Pennsylvania showed that only 6% (14 out of 218) of residential water systems were colonized with Legionella pneumophila, the bacteria that causes Legionnaires’ disease. This was the largest sampling of residential homes reported.

Our conclusions in Legionella pneumophila in residential water supplies: environmental surveillance with clinical assessment for Legionnaires’ disease show that even in a region known to have endemic hospital-acquired Legionnaires’ disease, the prevalence of Legionella was low and healthy adults don’t appear to be at high risk even when living in homes with contaminated water supplies.

Who is at Risk?

Our 2004 study, Legionella in Residential Homes, funded by the Environmental Protection Agency, showed that those individuals who acquired Legionnaires’ disease from home water systems were more than 70 years old or had an underlying disease such as cancer, leukemia or HIV.

How can Legionnaires’ disease be contracted at home?

While the overall risk is low, there are some sporadic cases of Legionnaires’ disease from home potable water. You can contract Legionnaires’ disease from drinking water through aspiration (“water going down the wrong pipe”) or aerosolization via humidifier or whirlpool spa. Showering hasn’t been shown to be a major disseminator of Legionella.

Where is Legionella found?

Testing is the only way to determine if your home drinking water systems has Legionella. Water samples should be drawn from your water heater and water faucets and showerheads.

How can you prevent Legionnaires’ disease in your home?

Preventative measures can be taken by disinfecting your water system such as: periodic thermal disinfection, point-of-use water filtration or boiling drinking water.

Thermal disinfection involves raising the hot water temperature to the maximum setting on the hot water tank (140°F [60°C]) and flushing each outlet for 20 to 30 minutes with the super-heated water. After the procedure return the temperature to the previous setting. Please note this is a short-term measure.

For more information or questions regarding Legionella in your home, please contact us or see the FAQ section on our educational website legionella.org.


First reported cases from home water systems

Legionnaires’ disease acquired from the water supply within the homes of two patients.

JE Stout, VL Yu, P Muraca. JAMA 257:1215 1217,1987.

Surveys of home water systems 

Legionella in Residential Water Systems. JE Stout and R.R. Muder. ASHRAE Journal. 2004; 46:52-54.


Potable water as a cause of sporadic cases of community acquired Legionnaires’ disease.

JE Stout, VL Yu, PM Muraca, J Joly, N Troup, LS Tompkins. N Engl J Med 326:151 155, 1992.


Legionella pneumophila in residential water supplies:  environmental surveillance with clinical assessment for Legionnaires’ disease. JE Stout, VL Yu, YC Yee, S Vaccarello, W Diven, TC Lee.  Epid Infect 190: 49 57, 1992.


Factors predisposing to Legionella pneumophila colonization in residential water systems.

TC Lee, JE Stout, VL Yu.  Arch Environ Health 43:59 62, 1988. Water filters.

Point of Use Filters
Kleenpak point-of- use water filters by Pall Medical provides a barrier against Legionella in your home.

Legionella testing
If you or a member of your family has or had Legionnaires’ disease, contact us by email or 412-281-5335 for information on Legionella testing.