I've been saying for some years now that the official program that was running to lower hot water cylinder thermostats to 50 or 55deg C would carry a very high risk of Legionnaires Disease in the future. but the "experts" have ignored me. Now the real facts are coming out!
If you have turned your cylinder down in the past, turn it back up to at least 60degC NOW. The risk is very real.
nzjay,
Oct 9, 2:22am
As normal hot water thermostats are only accurate to about + - 5 or 10deg, you really need to check by running a tap till hot and using an accurate thermometer to make sure you are getting 60deg C water. If your system has a tempering valve, so that tap water can only be 50 or 55degC, turn your thermostat up to 65 or even 70 to make sure that the stored water is above 60deg as a minimum.
wembley1,
Oct 9, 2:36am
What are you on about? The official advice IS to have cylinder temperatures above 60C!
Did you read the article? "Hawke's Bay District Health Board initially thought the woman may have contracted the disease because the temperature on her hot water cylinder had been set to somewhere between 50-55C.
But the board has since discovered that the gauge was misread, and that the temperature was actually set somewhere between 60-65C."
chitty11,
Oct 9, 2:50am
question about this I wonder if anyone can answer. If hot water cylinder temperature is set correctly say 70 deg for argument sake, in theory the legionnaires should not be able to survive in the stored water. But then come down to tempering valve after tempering valve water ends up being only say 50-55 deg which is the max our tempering valve can go as stated on the valve so would it be possible for the legionnaires to take hold in the pipe after the tempering valve? or would the on off flow of the water going through it prevent that from happening? Just a curiosity but maybe all those with a tempering valve should ensure they boil water before drinking? however article is a bit misleading as it states the cylinder was at the correct temp.
trad,
Oct 9, 2:56am
Do you catch Legionaires by drinking the hot/warm water or bathing in it?
ingies,
Oct 9, 3:11am
You could breath it in when you shower with the water.
trade4us2,
Oct 9, 3:33am
The new information is that having a tempering valve by the cylinder may cause Legionnaires. I have never had a tempering valve so I'm OK.
lm446,
Oct 9, 3:38am
The original outbreak of Legionaires disease occurred because the organism was resident in the water system of the hotel. Generally there is a recommendation that the water in the cylinder should be at 60c and the water at the outlet should be at 50c The whole drama is complicated by the fact that Legionella species is adaptive and evolves rapidly. In other words, today's precautions may be useless tomorrow. Also natural selection means that a new strain may take hold, and show some resistance to lower temperatures. Organisms, for example, are developing resistance to silver ions, sometimes used in hospitals to prevent Legionella colonisation. The 60c limit, by the way, is put there to prevent scalding in elderly patients. That temperature will not eliminate Legionella, merely stop growth. The organism can survive in blind pipes and also in biofilm (slime) The best approach, imo, is to keep calm and carry on. As long as water temp is above 50c at the outlet, that should be OK Bacterial evolution is a bitch. Listeria monocytogenes can grow well at 4c, survive temperatures around 72c, and grow happily in brine. -Oh yes, and use the threat of Legionnaires as a way of keeping shower time of teenagers and wives to a minimum
nzjay,
Oct 9, 4:14am
My advice is quite clear. The official advice a number of years ago, was to turn thermostats down to 55 (or on some early sites to 50) deg C. This has changed quite recently to 60 degC. There are still a huge number of cylinders out there that were changed to 50 or 55. Even at 60 degC, because of the inaccuracy of the thermostat (+ - 5 or 10deg, even setting at 60 on the dial may not be a high enough temperature setting. All the water in the cylinder needs to reach a minimum of 60 degC, at least overnight to safely immobilise lurking Legionnaires bacteria. In fact it needs more like 70 degC for several hours to be able to say that the organism is killed.
As long as the storage cylinder is up near 70 degC, any water in a pipe supplied by a tempering valve SHOULD not contain sufficient organisms to cause harm. Anything is possible with Legionnaires though, it is a resilient organism and can survive in nooks and cranny's. Farm (unchlorinated) water supplies are especially at risk if thermostats are set too low.
nzjay,
Oct 9, 4:19am
Only if the water feeding the tempering valve also contains the bacteria. Set your cylinder temp up to a checked 60 degC as a minimum and 70degC preferably, will greatly reduce the risk.
nzjay,
Oct 9, 4:23am
It's when it becomes airborne and is breathed in that it is at its most dangerous. It is basically a respiratory disease of a water borne bacteria.
nzjay,
Oct 9, 4:34am
The big trap here is that hotwater thermostats are inherently inaccurate, by as much as + -10 degC. In saying it was set at 60 - 65C could mean the cylinder temp may have been as low as 50C or as high as 75C. They make no mention of doing accurate tests of the temperature with a thermometer.
trade4us2,
Oct 9, 5:42am
Basically the new recommendations will likely be that if a tempering valve is fitted at all, it must be fitted right next to all showers. The rest is rather obvious so doesn't need discussion.
wembley1,
Oct 9, 6:01am
While some well-meaning energy conservationists may have said so, the Building Code "G12 Water Supplies" states: "6.14.3 Legionella bacteria Irrespective of whether a mixing device is installed, the storage water heater control thermostat shall be capable of being set at a temperature of not less than 60°C to prevent the growth of Legionella bacteria."
The above was lifted from the 2004 edition of G12 so as far as I can see the "official" advice has been 60+ for over a decade (at least).
wine-o-clock,
Oct 9, 7:00am
i'm still alive and my cylinder was set to 50° farenheit! its actually very hot in the shower!
nzjay,
Oct 9, 7:06am
Sure, that was buried in the Building Code, and how many ordinary public read that? The PUBLIC thrust, was purely to prevent scalding of young children and was very widely publicised, WITHOUT correction by the Building Authority. It was later picked up on by the energy conservationists and even more widely publicised. This is a typical case in this PC age where the left hand loses track of the right hand.
fantail8,
Oct 9, 7:14am
nzjay wrote: ". The PUBLIC thrust, was purely to prevent scalding of young children and was very widely publicised, . "
That is EXACTLY the reason why ours was turned down at our old place.
trade4us2,
Oct 9, 7:29am
All the diagrams that I have seen for the installation of a tempering valve show the valve next to the cylinder. That is now wrong. I hope somebody will redo all the diagrams and tell plumbers. I wish they would redesign the pressure relief valves as well, because they are unsuitable and need to be replaced often. The height of the cylinder should be specified also. They should preferably not just sit on the floor. Any plumbers care to discuss?
nzjay,
Oct 9, 8:26am
As I see it, there is nothing wrong with the tempering valve next to the cylinder, providing the cylinder is operating at a temperature than kills the Legionnaires bacteria. If there is no bacteria in the cylinder, how is any going to get into the pipe after the tempering valve?
gwimweeper,
Oct 9, 9:46am
Are you a polar bear ?
Or does your water somehow increase in temperature between your cylinder and shower head ?
skin1235,
Oct 9, 10:32am
you answered that one earlier, cold supply to the tempering valve is an unknown bacterial load, all points past that can be suspect
trade4us2,
Oct 9, 10:34am
The article said " there was a tempering valve between the hot water cylinder and the tap, and that the bacteria had grown in this part of the system." I assume the experts know what they are talking about.
skin1235,
Oct 9, 10:59am
never quite understood why they had to be fitted at the cylinder in the first place apart from convenience
surely 60 ish is not hot enough for washing dishes, could understand perhaps the voluntarily fitting then in the bathroom, showers and bath temps can be a risk with young ones, and aged, but insistence by law? crazy, are we that stupid we need laws and regulations on how hot we have our water in the cylinder, based on what sort/number of incidences? none fitted here and the wetback throws low pressure ( not mains pressure ) water over the roof at times
pauldw,
Oct 9, 6:50pm
I don't know where you've found advice to turn the cylinder down to 55C. I've only seen 55C mentioned in reference to the need for a tempering valve. The cylinder temp has always been a separate issue. Most example diagrams show the tempering valve only in the supply to the bathroom etc but apparently it was rare for kitchen and laundris to bypass the 55C supply.
Normally pipes would get flushed out with use. Maybe the problem pipes had a long stub that didn't get emptied very often.
hazelnut2,
Oct 9, 7:28pm
50F is NOT hot, body temp is 97F! Are you sure you're not reading 150F?
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