New bathroom - no hot water to shower? ok to sink though, combi boiler

[MrsB]

Hi,
If anyone has any suggestions I'd be really grateful... We have just had the bathroom refurbished, everything worked fine before but we needed to add a bath as there wasn't one. We have combi boiler, about 10 yrs old.

So, a new thermostatic mixer shower (Mira) has been added and a bath filler tap, but neither deliver hot water. It's hot for about 5-10 seconds then luke warm for ages before another dash of hot water and more luke warm water. Sink gets consistently hot water as does kitchen sink

Plumber reckons they have everything fitted fine. Boiler man reckons we need a new boiler (that's out of the question at the moment, as we just spent on new bathroom). I'm not convinved that i need a new boiler is necesary as the sinks seem to be working fine, could it be to do with the too high a flow of water to shower/bath tap? or valve settings? any viable solutions please?

Really wishing we hadn't started this project now, 3 weeks of no bathroom and not an end in sight :-(
Thanks in advance,
MrsB

 

[stoker122]

Does the temperature stabilise if you reduce the flow of water through the bath tap?

 

[stevetheplumber]

lack of non return valves or non return valves stuck shut ?

 

[Dan Masey]

As stoker said, turn the bath got tap down half way and see If it suddenly heats up and stays hot. I'm guess its a 22mm hot fees to the bath tap and then tee'd off for the shower above it. Too high a flow rate for boiler to cope with....?

 

[MrsB]

Does the temperature stabilise if you reduce the flow of water through the bath tap?

On the bath tap, if youhave it at medium flow then it's hot and goes to luke warm, but if I turn it right down so there is a really small flow than it does stay warm - but that's not exactly usuable. So, if the flow rate is too high, how can that be fixed?

I can't test this on the shower unit because the on/off is the same gauge as the temperature. Would it be best to just switch it to an electric shower? (although that doesn't solve the bath tap problem).

Thanks everyone! really appreciate it as the plumber and boiler man are blaming each other at the moment, so it's hard to know what to do!
Mel

 

[TBServices]

If you have to reduce flow to little more than a trickle to get HW, your boiler is probably in need of repair. Sounds like a blocked plate heat exchanger may be to blame.

 

[stoker122]

Haven't you got any money left from being in the spice girls
What sort of taps are fitted to the bath?

 

[MrsB]

bath tap is a 'round cascade waterfall mixer' it has separate controls for hot n cold.

Pressure on boiler is just under 2, and the tap only requires 0.5

Would have been right age for spice girls, but no sadly not!

 

[SJB6]

Like TBServices said if you have to reduce the hot tap to a mere trickle then its probably the boiler. Combi boilers will produce a maximum flow rate of hot water, your new bathroom taps and shower could be exceeding that flow rate which would cause that problem (tap and bath flow rates can be measured easily with a flow rate cup and the cross checked with boiler flow rates). The hot water flow rates from a combi can be adjusted quite easily without the need for a new boiler, potentionally, but all combi boilers will have a max flow rate limit.
I suggest you call another plumbing/heating engineer out and get a second opinion.

 

[SJB6]

A pressure limiting valve will solve that problem as well, there should always be a pressure limitig valve on pressurised systems anyway.

 

[stoker122]

Hi,
Sink gets consistently hot water as does kitchen sink

What is the flow rate like at these taps?

 

[PlumbBobBob]

the pressure gauge on the boiler doesn't refer to water pressure, it is pressure in the heating side of things.