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Legionella and Domestic Hot Water Systems

Dear Client,

Many of our clients do not realize that Legionella can live very comfortably
in warm water, up to about 122 degrees.  This means that it likes the
building's domestic hot water system.   We have visited several facilities
recently including medical facilities that have chosen to operate their
water heaters at 110 degrees, providing a potential breeding ground for
Legionella.  Building management and operators state that they want to save
energy or that they do not want to run higher temperatures that require a
mixing valve to provide code required temperatures to sinks, etc.

While we understand that budgets for operation and maintenance are under
pressure, we do not feel that this is an area that can be compromised.
Between 8,000 and 18,000 people are hospitalized each year from Legionella
with a fatality rate of 5% to 30%.

We highly recommend operating your domestic hot water system at 140 degrees
and using a quality mixing valve to reduce temperatures to a code required
level for use in your building.  In addition, during any renovation of your
facility, make sure that the contractor does not leave dead end or abandoned
piping in place that can result in stagnant water in the piping system.

If you have any questions regarding the design of your system or the quality
of your mixing valves, please give us a call.  We can help you evaluate your
systems deficiencies and design the appropriate solutions.

Sincerely Mark Fratto, P.E., LEED AP BD+C