told by plumber that a whole house mixing valve wont work?

[mpooley]

I just asked a plumber for a quote for fitting a whole house thermal mixing valve because our hot water is sometimes too hot.
He told me I would need separate mixers on every tap as a mixer by the tank would not work.
specifically he said water would get too cold by the time it got to the taps!

he said this without seeing my house or asking me any questions about my system.
I can't believe this is true.

is there any problem with a whole house mixer, I can't see any difference with water heated too 42c or blended to 42c I think the guy just doesn't want the job.

 

[ALEC1]

Well he may be right.. It all depends on relative lengths etc

But I would investigate and rectify the issue at source

 

[JohnD]

our hot water is sometimes too hot.

how is the HW heated? Is there a cylinder? What colour is it?

 

[leakydave]

Why is your water too hot?

 

[mpooley]

If you mean keep the temperature low in the first place i don't want to.
I have free electricity from my PV system.
What i want is to have a safe temperature at my taps.

thanks

 

[mpooley]

our hot water is sometimes too hot.

how is the HW heated? Is there a cylinder? What colour is it?

immersion heater and it's covered in buff coloured foam

thanks

 

[leakydave]

Can't you turn the immersion down?

 

[doitall]

Stored water should be a minimum 55c unless you run a monthly purge cycle

 

[robbieduncan]

Stored at 60C and distributed at at least 50C. So mixers on the taps...

http://www.hse.gov.uk/healthservices/legionella.htm

 

[doitall]

Stored at 60C and distributed at at least 50C. So mixers on the taps...

http://www.hse.gov.uk/healthservices/legionella.htm[/QUOTE]

Interesting link robbieduncan.

Thought it was reduced to 55c now.

This paragraph was helpful to the OP.

Using temperature control

The primary method used to control the risk from Legionella is water temperature control.
Water services should be operated at temperatures that prevent Legionella growth:

Hot water storage cylinders (calorifiers) should store water at 60°C or higher
Hot water should be distributed at 50°C or higher (thermostatic mixer valves need to be fitted as close as possible to outlets, where a scald risk is identified).
Cold water should be stored and distributed below 20°C.

A competent person should routinely check, inspect and clean the system, in accordance with the risk assessment.

 

[gigz]

Is it unvented ? Can't say for definite but if it is a blender valve should be ok, fitted to the hot outlet.

 

[SandyLyon]

You don't want to reduce the temperature at the storage point, better keep the temp high and fit a TMV as close as possible to each draw off point.
As previously posted long runs of tepid water can lead to serious healt threats.

 

[Dan Robinson]

Funny how when OPs get told something they don't like, it can't possibly be true.

 

[muggles]

Funny how when OPs get told something they don't like, it can't possibly be true.

...and sometimes they mysteriously disappear, presumably to see if they can get the answer they want on another site.


OP - from the TMV installation code of practise
"When one valve is used to supply mixed water to a number of outlets the length of the pipe run and the volume of mixed water after the valve should be kept to a minimum.

The maximum pipe run after the mixing valve should be such that the required mixed temperature, at the furthest outlet, is reached within 30 seconds"

 

[JohnD]

a yellow-insulated hw cylinder, so presumably is vented.