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Hi, everyone.

I have a shower in a bathroom that is about 100m pipe run from the boiler, and getting hot water to it without running the boiler stupid hot is a problem.

Is there an instant water heater that I can install to feed the whole bathroom that is compatible with TMV's and the thermostatic mixer on the shower? Most of the cheap ones that use flow rate to control the temperature explicitly state no, but I can't find any that definitely are OK.

Removal of the TMV's is not an option
 
I have - problem is the water in the pipe just isn't hot enough. Should be over 60° C and I'm struggling to get it above 50. Allowing for the 10° temp difference in to out on the tmv that makes for 40° at the shower head. That's a cold shower.

I should re-run the hot pipe but due to the building layout and modifications by the previous (commercial) owner that I can't easily remove, it's simpler to heat the water locally. It's only this one bathroom - the other 3 are fine. Half the building is on a hot loop - this bathroom is on a massive leg that isn't part of the loop. Ideally, I would install an inline instant heater in the feed pipe as the pipe runs pretty much over the consumer unit so wiring would be simple. But I can't use one unless it's happy with tmvs.
 

ShaunCorbs

Staff member
S. Mod
Plumber
Gas Engineer
Is the pipe insulated?

Also could you install a secondary return tee ?
 

Danb

Gas Engineer
Doubt youll get any tmv that goes above 49/50.c its a safety device.
If i read it wrong my apologies but have you got tmv prior to the shower!
 
Pipe is insulated - hasn't considered the secondary return.

What I think has happened is that a previous job has created a 'short circuit' somewhere between the hot feed for the bathroom and the existing secondary return.

Unfortunately I can't eyeball the entire pipe run to confirm this without tearing into the ceiling and several walls in a dozen places - although the site of a now-removed ensuite shower is a strong possibility.
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Doubt youll get any tmv that goes above 49/50.c its a safety device.
If i read it wrong my apologies but have you got tmv prior to the shower!
Yep there is a tmv on the shower - 50 degrees is indeed the max it can be set at and that would be just about OK.
You didn't read it wrong I wrote it wrong lol - the shower is a standard non thermostat mixer but there's a tmv in the hot feed.
There are also tmvs in the feeds to the bath and basin.
Regs only say there needs to be one on the bath, but I don't want to remove the others either as there are disabled adults and children in the house.
The basic problem is that the hot feed isn't hot enough for the tmvs to work properly so I'm looking for a temporary fix over the winter. Next summer when I can get into the loft without wearing every jacket I possess, I'll work out what I need to do to fix it properly.
 
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king of pipes

Esteemed
Plumber
Gas Engineer
Advent Win
Easy fix is connect a electrical trace heating tape to the pipework this heats the pipe and water inside and keeps it at a constant temperature by using a thermostat look at Raychem products or similar you may need to replace the insulation for the next size up ensure it is fitted correctly with no gaps and a good thickness ideally 19mm. Kop
 

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oz-plumber

Esteemed
Plumber
Can you get a gasline near the bathroom?
Could you install a continuous flow hot water heater?

Look up Rinnai water heaters - see if that can solve your issues
 

centralheatking

Esteemed
Plumber
Hi, everyone.

I have a shower in a bathroom that is about 100m pipe run from the boiler, and getting hot water to it without running the boiler stupid hot is a problem.

Is there an instant water heater that I can install to feed the whole bathroom that is compatible with TMV's and the thermostatic mixer on the shower? Most of the cheap ones that use flow rate to control the temperature explicitly state no, but I can't find any that definitely are OK.

Removal of the TMV's is not an option
is there a bath involved or is it shower, basin and bog centralheatking
 

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