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PLUMBING CONNECTION
SPRING 2016
optimum temperature for bacteria growth, over the last few
years Legionella bacteria have increasingly been discovered
in cold water systems. This is due in part to energy
conservation measures, particularly improved insulation in
new buildings, which promotes better heat retention and
reduces energy losses.
Cold water distribution systems are a natural heat shield
in buildings due to the temperature difference between the
system and the ambient air. As a consequence the water
within these systems becomes increasingly warm, rising to
a temperature which supports the proliferation of Legionella
bacteria.
A study of four healthcare facilities in Germany with cases
of healthcare associated Legionnaires disease, found cold
water samples taken from distal sites were more frequently
contaminated (40% vs 23%) and contained higher
concentrations of Legionella than warm water samples
4
.
This is despite only 5% of the cold water samples displaying
a temperature of over 25°C (the temperature at which
Legionellae multiply) at sampling time.
This may be due to the “warming up” effect of cold water,
which can occur after long periods of inactivity or when the
cold and warm water pipes are closely fitted in the same
shaft without appropriate insulation. This warming up
effect may not be detectable at the time of sampling, but
highlights the importance of regular assessment of cold
water systems.
WATER MOVEMENT AND PREVENTING STAGNATION
Regular movement of cold water around the distribution
system, and as close to the outlets as possible is necessary
to reduce the build-up of biofilm by preventing stagnation.
This also helps to keep temperatures low, slowing Legionella
growth.
LEGIONELLA
WHY AUSTRALIA MUST RETHINKWATER SYSTEMS DESIGN
LEGIONELLA IS A LINGERING, EVER-PRESENT BACTERIUM WHICH, IN THE RIGHT BREEDING CONDITIONS, POSES A
SIGNIFICANT HEALTH RISK. HOSPITALS ARE ONE OF THE HIGHEST RISK ENVIRONMENTS FOR LEGIONELLA AS THEY HAVE
LARGE AND COMPLEX WATER SYSTEMS COUPLED WITH THE VULNERABILITY OF PATIENTS WITHIN.
AN OPTIMUM TEMPERATURE FOR LEGIONALLA TO FLOURISH
NEW YORK
OUTBREAK
2015
2013
BRISBANE
HOSPITAL
12 DEAD
100 INFECTED
1 DEAD
1 INTENSIVE CARE
IN BRISBANE, TEMPERATURE CONTROLS MEANT WATER AT THE HOSPITAL COULD NOT REACH A HIGHER TEMP THAN 45ºC
BELOW 20ºC: LEGIONELLA CAN SURVIVE BUT ARE DORMANT
20-50ºC: LEGIONELLA GROWTH RANGE
50-55ºC: LEGIONELLA GROWTH RANGE
55ºC: LEGIONELLA WILL DIE IN 5-6 HOURS
60ºC: LEGIONELLA WILL DIE IN 32 MINUTES
66ºC: LEGIONELLA WILL DIE IN 2 MINUTES
70-80ºC: DISINFECTION RANGE