Plumbing Connection 2-2015

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4 0 PLUMBING CONNECTION WINTER 2015
in the hot water reticulation system are maintained to an
absolute minimum, the DOH nominates a minimum of 10
lineal meters or 2 litres of draw off. In our hydraulic designs
engineers normally aim to have even less draw off than this.”
KEEP IT CLEAN
The last tactic in the fight against biofilm is keeping the
water system clean. This can begin even before the water
has entered the building.
“Site filtration, UV disinfection and chlorination are used
and advised methods for incoming cold water supplies to
reduce the risk of breeding legionella and pseudomonas,”
Antonio states.
Once the system is installed, regular maintenance is
needed.
“Storage tanks should be inspected regularly and cleaned
and disinfected annually,” advises Antonio. “A close eye also
needs to be kept on automatic backwash filters and bag
filtration systems.”
The right materials can help keep the inside surfaces of
the plumbing fittings clean. Rada aims to eliminate plastics
and reduce the use of elastomers in their new range, as both
of these materials give bacteria a place to live and often
provide a food source.
“If you can optimise the product to make it entirely of
metal, you’d be doing a good job,” Kevin says. “Brass and
copper are the favoured materials because they have
antimicrobial properties.”
Copper and brass are more expensive, but with the
shrinking of the taps mentioned above, the amount of
materials needed (and the cost) is also reduced.
Perhaps the most challenging and labour intensive
method of keeping it clean is thermal disinfection. Even with
a thorough treatment system, legionella and pseudomonas
can make their way into a building’s water system – thermal
disinfection is one method of killing these invaders.
The first challenge is keeping the water hot enough to kill
bacteria. As discussed above, many of Australia’s hot water
systems are actually warm water systems and not capable
of maintaining the temperature required: at least 60°C, but
preferably above 70°C.
The second challenge is to avoid scalding anyone during
the process.
“At the moment, it seems like a very manual process,”
Peter explains. “Maintenance staff stand in front of the
shower and physically flush the system.”
There are moves to automate the system and have it
running when it’s unlikely anyone will be using those outlets
– for example, in the early hours of the morning. But in many
of these facilities, it’s impossible to ensure no one will be
using the outlet. Peter gives the example of an older lady
with dementia who might decide to have a shower at two
o’clock in the morning.
The Rada range has been designed to offer automated duty
flushing, but the risks presented by thermal disinfection require
a maintenance engineer to be present. Should they leave the
tap unattended before the cycle has finished, a safety feature
will terminate the disinfection cycle, if the tap’s sensor senses
a person’s hands approaching. But this is high-end technology
which will retrofit into most situations as long as a power cable
can be located near to the tap or shower.
THE ONGOING PUZZLE
The battle against bacteria is certainly an ongoing one. As
bacteria develop resistance to different antibiotics and adapt
to new environments, we will need to change our defences to
match. Plumbers and hydraulic engineers have many weapons
at their disposal; it’s a matter of finding the right ones for the
situation. As Antonio states, “It is crucial that pre-filtration
and treatment systems that are selected suit the end users’
needs and methods, otherwise they just don’t get used.”
The same could certainly be said for the water distribution
systems and other end use products. The tactics used must
suit each individual battleground.
Reliance Worldwide Australia
Thornthwaite Technologies, distributors of Rada
Wood & Grieve Engineers
INFECTION CONTROL
A TMV installation depicting the hot and cold water inlets.