Legionella bacteria are common. They can be found
naturally in water sources, meaning that they can potentially colonise in
manufactured water systems. If exposed to legionella
bacteria, humans can develop Legionnaire’s disease, a potentially fatal
respiratory condition.
Legionella bacteria
thrive at temperatures of between 20oC and 45oC, but die
relatively quickly at temperatures above 60oC. So, in order to eliminate
harmful bacteria forming in hot water storage systems, water is generally
stored and distributed at 60oC or above. However, water delivered to
a tap or shower at this temperature poses a serious scalding hazard, with water
at 60°Cbeing able to cause a partial thickness burn in about five
seconds.
The most effective way to
provide safe water temperatures while
eliminating the risk of bacteria is to store and
distribute hot water at a high temperature and use a Thermostatic Mixing Valve
(TMV) to control the temperature at the point of use.
TMVs reduce the discharge
temperature of stored hot water to an appropriate level by blending it with
cold water before it reaches the tap, ensuring a constant and safe outlet
temperature. The deadleg between the TMV and the hot water
outlet should be kept to a minimal distance. This will reduce the risk of
harmful bacteria being able to breed, and also helps to save water.
TMVs
are legally required in a number of environments, including for baths in private
and housing association dwellings, housing association dwellings for the
elderly, care homes for young people, schools (including nursery and those for
the severely disabled), and NHS hospitals. In other environments such as
private hospitals and care homes, their use is only recommended, and elsewhere,
it is regarded as best practice – for instance in hotels. It’s important though
to remember that scalding can cause serious injuries for any adult, and that
while guidance may not require TMVs by law, best practice should be followed
wherever possible.
Even when using TMV3
valves, it’s important to bear in mind that careful selection and maintenance
of the hot water cylinder is equally important when guarding against
legionella.
Products should be designed to meet the
requirements of the Health & Safety Executive’s L8 document (the approved
code of practice for Legionnaire’s disease). This strongly recommends that cylinders should be serviced and cleaned
periodically, so integral inspection hatches are of particular benefit. A
de-stratification loop to thoroughly circulate hot water is another major plus.
Cylinders like the Megaflo Commercial have been
designed with these requirements in mind. An optional de-stratification loop ensures the thorough circulation
of hot water, while 125mm inspection
hatches improve accessibility for servicing and cleaning.
Megaflo Commercial delivers hot water at up to 177
litres per minute at 6 bar pressure and 212 at 10 bar. The range of 48 cylinders
offers indirect, direct and solar versions, making it suitable for any
commercial application. Manufactured from 2205 marine-grade stainless steel, Megaflo
Commercial offers low thermal expansion and high chloride resistance. What’s
more, it has a great strength-to-weight ratio which allows the finished
cylinder to be substantially lower in weight than other materials, making
handling and installation easier.
All Megaflo Commercial units offer a 30 year
warranty.
For more
information on Heatrae Sadia’s Megaflo Commercial and TMV3 range, visit www.heatraesadia.com.
