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Maintaining hot water storage tanks at 120°F
while often recommended for energy conservation, may not be the
best for your facility.
Over the past several years, studies have indicated that warm
or tepid water systems may be breeding grounds for the bacteria
Legionella Pneumophila, otherwise known as Legionnaire's Disease.
One way to combat this potentially deadly disease is to maintain
hot water storage tanks at or above 140 degrees Fahrenheit.
The bacteria which causes Legionnaire's disease is often
present in many natural freshwater sources including lakes,
ponds, streams, and rivers--ultimately finding its way into
domestic water systems. Essentailly, it's in the water supply.
"Many of the outbreaks are occurring in hospitals, office
buildings, hotels, and other settings," said Henry Healey,
president of Healey & Associates, the engineering division of
The Florida Alternative Energy Corporation. "A person can
get the disease by either inhaling airborne water droplets
containing Legionella or drinking Legionella-contaminated water.
The risk can be high with humidifiers, showers, sinks, fountains,
or whirlpool baths, for example."
While Legionella is everywhere, the mere presence of it in the
water is not a cause for concern. Rapid growth, resulting in high
concentrations, is essential before the water can be considered
hazardous, Healey added. The key ingredients--a wet environment,
the presence of oxygen
and carbon dioxide, high microbial concentrations, scale and
corrosion products--as well as a favorable temperature range
(68 to 120 degrees Fahrenheit) must be present in order for the
bacteria to reduce rapidly.
"Unfortunately, many hot water storage tanks provide an
opportunity for accelerated reproduction or bio-amplification.
You have to keep the water conditions at temperatures where the
environment is not favorable for growth to Legionella out of the
water," Healey added. "Hot water should be stored at
temperatures no lower than 140 degrees Fahrenheit and deliver hot
water at a minimum of 122 degrees to the outlets."
While there is little chance of scalding at that temperature (122°F),
an anti-scald valve can be installed at the outlet of the water
heater. "An anti-scald (not a tempering valve) helps reduce
the minimal risk of scalding for children or individuals with
disabilities," Healey said, "It is highly recommended."
Keeping your facility out of risk is key to avoiding
outbreaks, he added. Establishing engineering and management
policies regarding the selection, installation, cleaning
maintenance, inspection and sampling is a good way to keep
Legionnaire's Disease out of your facility.
For more information on facility management practices designed
to minimize problems and operating, email flaenergy.com with your
request and we will respond. We routinely assist facility managers
in the development of preventative to avoid problems and control costs.
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