Cold water is not cold- and Legionella know it!

Here's a few insights into what we rather loosely term ' cold water' in large buildings. I'm sure that in some locations cold water is very cold. I vividly remember my pipes freezing in winter in the UK - and once (for a few days) the toilet bowl iced up too!! But in other locations cold water only gets below the 'magic' 20 Celsius for a few months of the year.

The 'Magic' 20 Celsius

I call it 'magic' - because it is a number that actually has no evidence behind it! A thorough search of the published literature will draw a blank with regards to Legionella multiplication below 20 Celsius. It's just a number that public health people and then regulators settled on as a 'rule of thumb'. At the time, with a lack of evidence, that was necessary. Now it is enshrined in legislation! (Left: Thumb kindly donated by my left hand).

Rule of thumb does not require evidence, but often quite quickly becomes laid down in regulation. After a while we believe the regulations have some evidence behind them. So if you check the regulations; often 'cold water' is not a problem - but the regulations also struggle to tell you what cold is.

Why does this matter? It's about what 'cold' is. Go find a useful definition of cold water. After that ask yourself whether Legionella bacteria agree with you - or the regulations? My feeling is the bacteria themselves are oblivious.

To be a little provocative and facetious - many failures of regulation have been about failing to communicate with the bacterium in question! The poor little critters just didn't understand!

To support this notion we have documented cases of disease from ice machines, chilled water fountains, decorative fountains etc that have never been supplied with heated water. Of course they may have become warm in the process - but that's another story...read on! There is good evidence that Legionella will multiply above 20 Celsius - and well into the 40's, and perhaps beyond!

The Supply

There is no doubt that the major route of contamination of all building water systems is the mains (cold) water supply. Responsibility of the utility for that water supply stops at the meter and then becomes your problem.

Once it enters your building the water is at the mercy of ambient temperature and it's residence time. It will steadily move towards building ambient temperatures. This is not just temperatures in accommodated areas, but ceiling spaces, storages, conduits all of which can reach and sustain temperatures well above ambient for prolonged periods.

The nett effect is that your cold water is as much a risk as warm and hot water. Not only that, it probably feeds warm and cold water constantly.

The Outlets

This is where the rubber meets the road. Outlets are often the major source of exposure during disease outbreaks. Sadly outbreaks of disease have been attributed to cold water outlets with dead legs (not flushed) of less than 30 cm.

Ultimately in health and aged care it's Grandma, Grandad, Aunty, and Uncle, the immune compromised (the list goes on) that get the cold water; at a shower, a basin, a drink. If you forget the cold water you put them at risk.

What does that mean to me?

Well, sadly it means rather a lot. There is not time in this blog post to go into detail. But here's some questions for you to consider?

What do I do if my cold water isn't 'cold'?

What does this mean for my TMVs and their operation?
How will I go about disinfection?
Is this in the risk management plan?

What should I do?

Firstly start monitoring your cold water temperatures - pretty obvious huh? My guess is that pretty soon you'll realise you're above the magic 20! Then make cold water move. Flushing is the cheapest proven intervention at your disposal.

After that get an active and operational risk management plan. Look at your hierarchy of control. Decide whether disinfection of your cold water is something you should consider.

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