Page 9 - Water_Controls_for_Healthcare

HOSPITAL
Infection control / SOLUTIONS

COLD WATER TEMPERATURES OVER 20°C: BEWARE OF THE DANGERS!

Legionella, Pseudomonas aeruginosa and Mycobacterium To control the risk of bacterial proliferation in DCW pipes, action
avium are pathogenic bacteria that are present in drinking water must be taken at two levels: manage water temperatures
distribution systems in Buildings open to the Public. and prevent stagnation.
Various regulations and guidance point the finger at these bacteria, This requires a two-pronged solution:
and impose strict measures to control the risk of their proliferation, - air-condition the technical ducts so that the ambient temperature
focussing specifically on domestic hot water (DHW). For more of the technical area does not increase the DCW temperature.
information see page 4. Insulating DCW and DHW pipes then takes on its fullest meaning.

But what about cold water? - flush the DCW pipework regularly to avoid stagnation. The guidance
Cold water above 20°C can also be a source of bacterial is also very clear in respect of this, since it indicates that stagnation
development. According to Health and Safety Executive (HSE) is a significant factor in the development of biofilm and therefore in
Technical guidance HSG274 Part 2, 2024, the maximum the proliferation of bacteria in water.
temperature of cold water in the system should be 20°C. But in the DELABIE’s electronic basin taps, WCs and showers incorporate a
majority of healthcare establishments and retirement homes, the duty flush which activates the valves automatically if they have not
ambient temperature is usually maintained above 20°C. been used for 24 hours, preventing long-term water stagnation, in
accordance with current guidance.
Published in the medical journal Eurosurveillance, a study into
hospital cold water distribution systems reveals that 35% contain These two combined solutions can be easily implemented in most
Legionella in water at 20°C. This shows that cold water at 20°C existing installations.
already places the system at risk!
Hot water/cold water cross flow is a significant risk
Patients in healthcare facilities and retirement homes are, therefore, The problem of elevated cold water temperatures can be the result
exposed to a higher risk from waterborne pathogenic bacteria of cross flow between the DHW and the DCW at the point-of-use,
not only in the summer, but also all year round if the temperature due to faulty non-return valves. If this is the case, hot water can flow
in the technical area is persistently above 20°C; with a risk of the back into the cold water supply pipes, increasing the temperature
domestic cold water (DCW) temperature reaching 25° or even 30°C and resulting in bacterial proliferation.
in summer. However, it is almost impossible to regularly and systematically
Conclusion: at 20°C, beware of the danger! check the non-return valves on the mixers, unless you have a large
budget and a lot of staff.
How to limit the temperature of cold water in the pipework?
One solution consists of refrigerating the cold water using a The DELABIE solution: thermostatic mixers without
distribution loop and a cooling system, but this solution should be non-return valves
avoided because it doubles the length of the DCW pipework, which To overcome this difficulty, DELABIE has designed a thermostatic
amounts to doubling the surface area of the biofilm and, therefore, shower mixer without non-return valves, which prevents any cross
doubling the risk of proliferation. flow between the DHW and DCW. It protects patients against the risk
Moreover, this requires complex and very expensive DCW cooling of scalding from DHW at 55°C if the cold water supply fails, and also
equipment, with daily monitoring to ensure it is operating correctly, reduces the risk of bacterial proliferation thanks to its mechanism
and regular maintenance. Ultimately, this option is only possible for with no non-return valves and its design.
new-build projects. For more information see page 110.
Insulating the DCW and DHW pipes is essential, but this is not
effective if the DHW and DCW pipes are close to each other and
confined in the same space (i.e., in technical areas or chased-in
pipes) where the DHW is circulated above 50°C (55°C in healthcare
facilities), as recommended by HSE guidelines, which causes the
air temperature in the technical duct to rise sharply. The DCW then
reaches temperatures close to the air temperature of the technical
duct despite good insulation.

Hospital solutions 7