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Central Heating

New build...bath hot water tap is only lukewarm, rest if the taps are red hot!

I have just moved into a new build and the bath tap only every gets Luke warm and not hot enough to have a bath. All the other hot taps in the house produce extremely hot water but not the bath tap. I have tried turning down the flow and no matter what the flow, temperature still remains low. I have resorted to filling the bath with a pan from the sink as the tap in the sink is red hot!

The boiler is new and is a Worcester 34cdi green star classic combi boiler and is situated right next to the bathroom if this helps.

3 Answers from MyBuilder Heating Engineers

Best Answer

The only suggestion I can think of at this moment is, the heating & plumbing sub-contractors may of fitted a thermal mixer valve or blender valve, allowing the hot & cold water temperature to be regulated. Worth taking a closer look behind bath panel.

Image of mixer valve:

Mixer valves have a temperature adjustment (usually located at the top of the valve). Typically, this can be adjusted to change the position of the piston and therefore the proportion of hot and cold water entering the valve. Unusual to find this equipment fitted in a domestic property but certainly a probable cause.


Answered 7th Sep 2014

Yes, I agree with James. Sounds like you have a blending valve fitted below the taps to your bath. This is part of the new building regulations that state all new builds should have them fitted. They can be adjusted but they are usually limited to 43 oC. That should be hot enough so it could be the one you have is either faulty or not very good / cheap.

If you remove it you may be contravening building regs so you could try getting a better one?


Answered 29th May 2015

I would agree with that also so would try taking the valve to it's maximum adjustment. It's a P.I.T.A, but regulation now to prevent the risk of scalding.


Answered 3rd Dec 2016

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