Water temperature

Hi All,

Wondered if I could get some advice on our home water temperature.
In a nutshell I want to lower it because it seems to be way too hot (even with dish washing gloves on I can't leave my hands in the hot water for more than about 5 seconds.
We have an old Valliant boiler (with no manual) which works the heating and hot water as far as I can tell. There is a black knob on the front currently set to 7. I'm thinking of chalking it back to 5.

I've also heard you need to keep your water temperature above 60C to kill Legionella? Is that for real?

Thanks for any help.

To prevent legionella bacteria the hot water needs to be 50 degrees at the outlet within a minute of opening the tap. The cold water needs to be below 10 degrees within 2 minutes.

To achieve the 50 degrees it is normal to store the hot water at 55 or above. To prevent scalding thermostatic mixing valves can be fitted within 2 metres of the outlet.

Great thanks Mike.

Do you think the knob/dial thing I'm refering to is simply a temperature control?

If its a combi you have legionella is not really an issue as there is no stored water
the recommended temp for cold water is less than 20 degrees not 10 as mentioned, during warmer weather you could run a tap for hours and not see temps off less than 10

How water temperatures affect Legionella:
[code:1]
70°C to 80°C - Disinfection range
66°C - Legionella die within 2 minutes
60°C - Legionella die within 3 minutes
55°C - Legionella die within 5 to 6 hours
20°C to 45°C - Legionella multiply
20°C and below - Legionella are dormant[/code:1]

The HSE Guidance for Employers is worth reading. Two things which may be of interest are:

"Infection is caused by breathing in small droplets of water contaminated by the bacteria. The disease cannot be passed from one person to another."

" They thrive at temperatures between 20°C-45°C if the conditions are right, eg if a supply of nutrients is present such as rust, sludge, scale, algae and other bacteria."

It's what you breathe in, not what you drink, which is important. So shower heads need to be kept clean.

I think on some combie boilers you can set the HW temp and the CH water temp separately. Look up your model on the manufacturer's web site.

The HSE Guidance for Employers is worth reading. Two things which may be of interest are:

"Infection is caused by breathing in small droplets of water contaminated by the bacteria. The disease cannot be passed from one person to another."

" They thrive at temperatures between 20°C-45°C if the conditions are right, eg if a supply of nutrients is present such as rust, sludge, scale, algae and other bacteria."

It's what you breathe in, not what you drink, which is important. So shower heads need to be kept clean.

Click to expand...

Sorry for hijacking this thread.
So my combi boiler isn't okay set at 45C?

David937 said:

So my combi boiler isn't okay set at 45C?

Click to expand...

If that is the maximum Domestic Hot Water temperature, there is nothing to worry about as the water is not being stored but heated straight from the mains, which will normally be about 10-15C.

Most combi boilers only raise the temperature by 35C. So, in the winter it can raise the temperature from, say 5C, to 40C; but in the summer, when the cold water temperature is, say 20C, it will only raise it by 25C to the 45C limit you have set.

If you are saying that the boiler temperature for central heating is 45C, there is still nothing to worry about as the central heating water and the domestic hot water are completely separate - they never mix.

Edit:

The Vaillant 937 has automatic Legionella protection - unless you have turned it off. This will raise the temperature in the storage tank if it falls below 50C. Though, as they warn in the manual, this could give rise to scalding. What a choice!