It has been long understood that ‘dead legs’ in plumbing systems are the major cause of legionella outbreaks and that they need to be designed out of the system to eradicate the problem.
Traditional T-piece plumbing systems have been identified as a significant contribution factor in the promotion of legionella due to their tendency to collect and stagnate water, which can provide an ideal breeding ground for the bacteria, which thrive in temperatures between 20oC and 60oC.
Mark Dowdeswell, Applications Manager and an expert in plumbing at Uponor, says the UK heating and plumbing industry needs to rethink its design and installation methods to minimise the risk to health.
“T-piece plumbing creates dead legs where it is possible for water to stagnate and breed the legionella bacteria. Unfortunately, the industry remains largely unaware of the dead leg problem, the risks associated with it, and the alternative plumbing methods which can eliminate the threat.”
In the UK more than 350 legionella outbreaks were officially identified in 2010 with 10 of these cases resulting in fatalities. A typical outbreak occurred in a plumbing warehouse in Stoke-on-Trent where a hot tub was identified as being the cause of 19 illnesses and one fatality.
However, flushing the system does not necessarily eradicate the problem, warns Mr Dowdeswell. “Dead legs are often immune to flushing as they can inhibit the exchange of water. Similarly, temperature control is no guarantee because the dead legs in a system allow water to cool to a temperature where the bacteria can begin to grow.”
CIPHE guidelines state that the length of any dead leg should be limited to six times the pipe’s diameter, more commonly known as the six diameter rule.
Mr Dowdeswell, says that these are not enough. “We have guidelines, but that is all they are, a guide not a formal regulation. If we are truly serious about eliminating the dead leg problem we need to look at alternative plumbing methods, such as loop and serial installation techniques, which are the methods used in Continental Europe to great effect.”
He continues: “Loop and serial installations are more hygienic than traditional T-piece systems because the risk of standing or stagnant water is significantly minimised. We need an industry-wide effort involving the CIPHE and manufacturers to get this message over and, if necessary, offer the training plumbers and installers need to eradicate this problem.”
For more information about Uponor please visit www.uponor.co.uk
