hot water temperature

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Re: hot water temperature

Post: # 169543Post Green Aura
Fri Sep 25, 2009 11:47 am

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Re: hot water temperature

Post: # 169598Post MuddyWitch
Fri Sep 25, 2009 3:09 pm

I 'googled it' as my tank is heated by a solar panel & the stove & the temperature varies dramatically. (I just looked & it's at 49.5 deg. C at the moment) I'm with Rosie though, & given the choice (back in the gas heated days) I always turned ours down to 48 deg C as any hotter & I'd scald myself or, worse, the kids.


Legionnaires’ disease is caused by a type of bacteria called Legionella pneumophila. The bacteria got its name in 1976, when many people who went to a Philadelphia convention of the American Legion suffered from an outbreak of this disease, a type of pneumonia. Although this type of bacteria was around before1976, more illness from Legionnaires’ disease is being detected now. This is because we are now looking for this disease whenever a patient has pneumonia.

Legionnaires' disease can have symptoms like many other forms of pneumonia. Signs of the disease can include: a high fever, chills, and a cough. Some people may also suffer from muscle aches and headaches. Chest X-rays are needed to find the pneumonia caused by the bacteria, and other tests can be done on sputum (phlegm), as well as blood or urine to find evidence of the bacteria in the body. These symptoms usually begin 2 to 14 days after being exposed to the bacteria.

A milder infection caused by the same type of Legionella bacteria is called Pontiac Fever. The symptoms of Pontiac Fever usually last for 2 to 5 days and may also include fever, headaches, and muscle aches; however, there is no pneumonia. Symptoms go away on their own without treatment and without causing further problems.

The bacteria are found naturally in the environment, usually in water. The bacteria grow best in warm water, like the kind found in hot tubs, cooling towers, hot water tanks, large plumbing systems, or parts of the air-conditioning systems of large buildings.

People get Legionnaires' disease when they breathe in a mist or vapor (small droplets of water in the air) that has been contaminated with the bacteria. One example might be from breathing in the steam from a whirlpool spa that has not been properly cleaned and disinfected. The bacteria are NOT spread from one person to another person.
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Re: hot water temperature

Post: # 179681Post matt_w
Sun Dec 06, 2009 10:03 pm

As far as I can tell reading between the lines of all the alarming hype, if your tank has the bacteria present it's still pretty hard to get infected by it as you have to inhale it through an atomised water droplet.

Our shower is electric mains fed, so simply put I personally think the chances of us having a problem with legionnaires is less likely than us winning the lottery (and we dont buy tickets!).

Our 'stat was set at 45 degrees (the worst temp for bacteria growth!), which was enough for one bath and some hand washing (we dont bath much, instead use shower). However since the summer this year we decided to turn off our (gas fired) hot water for summer. Now it is winter, still not turned back on and we still hardly miss it. When Mrs Wastell fancies a bath she puts the water on for an hour, which is about once every 2 weeks.

I really want to put in solar water heating, but Mrs Wastell keeps talking about return on investment and will we live here for long enogh etc... :?

The best bet reading the other post and putting 2 and 3 together, would suggest to me, you want a smaller hot water tank with better insulation* and a higher temperature to heat to with these thermostatic mixing do-dads so you cannot burn yourself. So perhaps insteam of 200 litres of 45 degree water, you want 150 litres of 80 degree water.

*The hotter something is above ambient, the more heat it looses over a given period of time than something cooler, so the better insulation you need to counter it.

My parents always kept the temp down on theirs so that no one could burn themselves. Of course anecdotal evidence from me, means nothing, your mileage may vary etc etc.

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Re: hot water temperature

Post: # 179807Post Thomzo
Mon Dec 07, 2009 9:43 pm

Ok, so can I just check I understand this:

Heating water above 60C will kill off most bateria, including the bacteria that causes Legionnaire's disease. Bacteria is present in water, even water that has been treated with chemicals. It is usually present in very small quantities that would not pose a problem but multiplies rapidly in warm environments.

Heating water to above 60C will use more energy than heating it to 47C but you use less of it when you fill a bath or washing up bowl as you add cold water to bring the temperature down. However, if your tank isn't extremely well insulated, you will lose more energy. You will also lose heat in the pipe between the tank and the tap unless that, too, is insulated.

Presumably, if you are washing up at 45 - 47C you won't be killing off the bacteria?

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Re: hot water temperature

Post: # 179850Post Greenbeast
Tue Dec 08, 2009 11:52 am

thomzo -
i believe you've understood the situation correctly

i must add, now that the solar isn't contributing and we're just using immersion, we rarely heat to 60C, because it does just dissipate before it'll next get used.

But then we don't use the heating so the house is very cold

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Re: hot water temperature

Post: # 180781Post MKG
Thu Dec 17, 2009 5:01 pm

Stop panicking - it isn't usually there at all. It occurs mainly in volumes of water which are not disturbed for extended periods of time. Household tanks are disturbed all of the time, so there is very little likelihood of an infection. Not impossible - just very unlikely.

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Re: hot water temperature

Post: # 180803Post Jandra
Thu Dec 17, 2009 9:02 pm

As far as I know the legionella bacteria lives in small concentrations in the soil and in water. It becomes dangerous when the bacteria has opportunity to multiply. Favourite temps between 25-55 Celcius, preferably in still water (hot water reservoir, little "lee" nooks or corners in the warm water piping).

I don't think anyone can say they never got legionella, as the symptoms very closely resemble a nasty flu. It doesn't always develop into a full blown pneumonia veterans disease.

Infection takes place through infected droplets of water in the lungs, not through ingestion. Showers, vapour from whirlpools etc. We had a major outbreak in the Netherlands about 10 years a go at a big flower show. The source was a bubble bath on display. 2000 people infected, 32 died, a number of people will continue to experience health problems the rest of their lives. I didn't know any people who got sick, but it was big news for a long time here so everyone who watched the news got a 'legionella primer' I suppose.

If I had a geyser or electric heater (hot water is heated and used immediately, never stored) I'd never worry about the temperature. But we now have a hot water tank and I do make sure the temp is set at 60 C. Energy well spent, I believe.

The water companies make sure that drinking water gets to us without harmful concentrations of germs, but it only takes one to tango, if you're a bacterium. So people are instructed to keep temps at 60 C and are responsible for their own safety in this matter, I guess.


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