Hot water not so hot... help please

30 Mar 2007
Reaction score
United Kingdom
Hi there...

My dad and I have recently installed a new bathroom in his house.. The hot water is fed by a new combi boiler that produces really hot water at a massive rate.. its brilliant...

We installed the sink, hot water was HOT!
installed the bath, hot water at both HOT!
installed the new shower cabin..... water luke warm.... :(

The utilities are sourced from the same supply, each spuring from the hot and cold pipe as necessary.

I am wondering if the shower cabin, needs no return valves on the supply pipes..? the hot and cold both go into a mixer and im wondering if its mixing in the shower valve and sending cold water down the hot pipe.... is this plausable?

To go from boiling hot to luke warm simply from the fitting of the shower seemed a bit bizarre and thats the only reason i can think of why it would happen. Does anyone else have any idea or fixes please?

Thanks in advance
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Chances are that it's a faulty mixer on the shower allowing cold to mix with the heated water. Is the shower designed for combi use, and is it piped correctly?
yes, its designed for combi use at a minimum of 1.5 bars pressure. Ive asked my dad to make sure the boilers pressurised fully as we have done new rads and things.....

Again, ive asked him to check the piping... we did quite clearly mark hot and cold feeds, but it was quite late when we got to attaching them so Ive asked him to check...

Am i right in thinking that the inlets shouldnt need non return valves on them should they..?


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