Water Temperature, Scalding, and Legionnaires’ Disease
temperature and its impact on the incidence of scalding and Legionnaires’ disease
is a hot topic in the industry at the moment. The issue is being
discussed at Plumbing Code hearings and not a month goes by that
the subject is not mentioned in the trade magazines. We have
assembled a range of information here related to the issues.
We hope you find it interesting and informative.
the bacteria that causes Legionnaires’ disease
requires raising the temperature of water to at least 140°F
- But, at
the temperature 140°F (60°C), water can cause
third-degree burns in children in one second and adults in five
- The U.S. Consumer Product Safety Commissions states that approximately
3,800 injuries and 34 deaths are directly related to dangerously
hot tap water in residences (The National Safe Kids Campaign
lists the number of scalding injuries as high as 6,500).
- The answer
to preventing both Legionnaires’ disease
and harmful water temperatures is to store the water at a high
temperature and temper it to a safer temperature before distribution
to the fixture.
- Legionnaires' disease acquired its name in 1976 when an outbreak
of pneumonia occurred among persons attending a convention of
the American Legion in Philadelphia.
- The bacterium is spread through inhalation, which can occur
while showering, washing or drinking the water.
- An estimated 8,000 to 18,000 people get Legionnaires' disease
in the United States each year (5% - 30% of the cases are fatal).
- Legionnaires' disease can cause fever, chills, and a cough,
which can be dry or may produce sputum. Some patients also have
muscle aches, headaches, tiredness, loss of appetite, and, occasionally,
diarrhea. Legionella may also cause cases of pneumonia that may
be difficult to diagnose.
- Improved design and maintenance of cooling towers and plumbing
systems to limit the growth and spread of Legionella organisms
are the foundations of preventing the disease.
Conditions For Legionnaires’ Disease
Pneumophilia, the bacteria that causes Legionnaires’ disease,
thrives in warm, stagnant water.
- A water
temperature of 120°F does not kill the bacteria;
a minimum temperature of 140°F is required.
- A water
heater set at 120°F can contain water as low as
- To eliminate
the bacteria, several steps need to be taken, including eliminating
dead-legs and system flushing. But, without a storage temperature
of 140°F, all other steps cannot solve
in Residential Environments
- In a recent test, 24% of a 21-family test group was found
to have Legionella bacteria in their home water.
- A combination of new and old research now suggests that the
bacteria may thrive in residential hot water pipes, and the water
supply used in residential homes may be directly responsible
for 20% of Legionnaires cases.
- Bacteria in natural water sources (not unlike those used by
residential dwellings) do not undergo the processes of filtration
and chemical disinfection that municipal water supplies go through.
Instead, natural water sources must be treated by the private
owner, a process which is often inconsistent or incomplete.
Leaps Ahead of the U.S.
- A change
has recently been made to Canada’s plumbing
code that requires water supplied to fixtures in residential
buildings to be a maximum temperature of 49°C (120°F).
- The change is expected to be adopted by January 2004 and fully
implemented by mid-2004.
- The reasons
for changing the code are listed specifically as the prevention
of scalding and Legionnaires’ disease.
- The solutions stated in the code are installing a TAFR device,
a mixing valve at each individual fixture or a master mixing
valve at the water heater.