Condo Media - November 2018 - 48

The Region

MAINE

Temperature
Matters
Is Your Condo in
Hot Water?
[by Jack Carr, P.E., RS, LEED-AP]

Is your hot water safe? If it's too hot,
you can be seriously burned. Not hot
enough, and your hot water may harbor
dangerous bacteria. What is the "correct" temperature to set a water heater?
It is a complicated question widely
debated, as "correct" depends if you are
concerned about energy saving, good
health, or safety.
From an energy conservation point of
view the Department of Energy's (DOE)
recommendation of setting the temperature at 120 degrees is the answer, as it is
also a much safer temperature to avoid
scalding accidents. However, the health
industry recommends 140 degrees, as
this setting is needed to kill Legionella,
the bacteria causing Legionnaire's Disease, which kills 10 percent of those who
become infected.
LEGIONNAIRE'S DISEASE RISK
People can contract the disease by
inhaling droplets of water containing
the bacteria. Most of the reported outbreaks have occurred in large institutional structures (hotels and hospitals)
and multifamily dwellings served by a
central water supply. Several cases have
been traced to evaporation from large
cooling towers. The Legionella bacteria
can grow in any water environment in
which the temperature is too low to kill
it, making it a potential risk in singlefamily condo units as well, hence the
debate over hot water heaters.
At 140 degrees, Legionella dies
within about 30 minutes while at 130

CONDOMEDIA November 2018

degrees it takes six
to eight hours for
the same result.
At the typical 120 degree
setting, the bacteria will survive
but not multiply. Below 120 degrees,
the bacteria thrives. These environmental health numbers then need to
be weighed against the fact it takes
10 minutes for water heated to 120
degrees to cause a serious burn while it
only takes six seconds of contact at 140
degrees.
The dilemma is that those most susceptible to the disease, namely people
with chronic respiratory disease or a
compromised immune system, are the
most likely to be scalded by water at
140 degrees. Adding to the problem is
DOE's estimate that households can
reduce energy costs by 10 percent by
turning the water temperature down
to 120 degrees from 140. So what's a
responsible property manager or unit
owner to do?
MANAGING AND
CONTROLLING RISK
One can argue the risks of contracting
Legionnaire's Disease is small-only
18,000 cases are reported annually in
the United States, compared to its population of 326 million. However, it you
do not want to make this risk-benefit
decision, you can install temperatureregulating devices either on the water
heater or individually on any taps used
for washing or bathing.

A thermostatic mixing valve attached
to the water heater injects cold water
into the heated water coming from
the tank, allowing you to set the tank
temperature higher than the water that
comes out of the shower or sink faucets.
Water tempering-pressure-balanced
valves attached individually to the faucets adjust the ratio of hot to cold water
coming from the taps to maintain the
temperature you select.
Although thermostatic valves are
more expensive-from $150 to $250,
compared to less than $50 for some
tempering valves-you only need one

The dilemma is that those
most susceptible to the
disease, namely people
with chronic respiratory
disease or a compromised
immune system, are the
most likely to be scalded
by water at 140 degrees.

Condo Media - November 2018

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