BEAMA

Mr Raper’s article suggests the Department of Health continues to favour temperature control as the best form of control of Legionella,inferring that by not recognising his organisation’s own system they are putting public health at risk.

His argument centres on the wording in HTM 04,which says that a temperature regime is the ‘preferred’ method of controlling Legionella in hot water systems, and what he would like to see is the word ‘traditional’ in its place. He claims there is no scientific evidence supporting a temperature regime.   

His organisation suggests on its website that they have 40 case studies/scientific papers to support their system. Only available on request, surely these should be centre stage on their web site.                    

The article highlighted a Parliamentary debate and related independent review with an extract from the final report suggesting ionisation with copper & silver was effective and safe in eradicating legionella. Unfortunately the quote was incomplete as it went on to say: “.. provided ion concentrations are kept within the appropriate range, pH is below 7.6 and scale is removed”. This is an important omission as scale has to be regularly removed from the electrodes and dosing must be monitored to avoid staining of water and sinks. Ionisation is affected by pH and Legionella control can fail, despite adequate copper and silver levels, if the pH level is too high.

A quoted ‘expert’ condemns mixing valves, because bacteria can proliferate downstream of them, that they are costly to install/maintain. The inference is that you can remove the mixing valves, run the system at a nominal ‘safe’ unspecified temperature and save money. This doesn’t consider the practicalities or whether a low temperature system is a workable, desirable or proven solution.

Any knowledgeable system designer would consider the suggestion you can run an entire system at low temperatures as absurd.

TMV’s are a mature proven solution, third party accredited to an NHS model engineering specification and a British Standard. The same cannot be said for silver copper ionisation.

While TMV’s are not the controller of Legionella, they allow systems to be controlled by temperature. Whether temperature or water treatment is used, poor system design and/or maintenance will result in bacteria breeding (via dead legs, scale, system debris).

Ignoring the fact that water/building regulations stipulate water must be stored at no less than 60 and circulated at 55 degrees, if the ionisation system operates at 40-45 degrees and stops working, the temperature would support bacteria growth. 

Controlling the system with heat means you know immediately if something goes wrong - there will be no hot water. If the ionisation system stops working you will have no warning; testing the water’s quality and that the system is working must be done more regularly - at significant cost.

We believe temperature is the best way to ensure bacteria is killed, as specified in L8 and HTM04, but neither document precludes silver and copper ionisation and as an additional level of protection it certainly has its uses.

HTM 04’s premise is to keep hot water hot, cold water cold. The temperature of hot water, 60 degrees, has been around some time and historically is nothing to do with Legionella. It is because hot water should be …hot.  Where people are at risk it should be controlled.

Running a system at a reduced temperature to save energy and to prevent scalding is not workable. Different outlets in hospitals require different temperatures; recommended temperatures for showers at 41 C, baths at 44 or 46 C etc. Some areas will have staff- only access, requiring high temperatures for hygiene reasons.   Bed pan washers, slop sinks, cleaners’ cupboards, kitchens etc require hot water - not lukewarm water.                 

These are likely to be in the same ward areas where patients need protection from scalding. The article’s scenario means installing two complete plumbing systems - one low temperature to prevent scalding, one high temperature maintaining correct hygiene.                                                   

A better, low cost, solution is to run the whole system at a high temperature - and to protect the vulnerable - by fitting TMV’s.

The Thermostatic Mixing Valve Manufacturers’ Association has developed a more detailed Q&A section aimed at dispelling the myths of Legionella control, click here for more information.