More mixer shower woes

message from Andrew Collins on 14 May 2004

I've been hoping to install a mixer shower, the problem I have is this
- the boiler (Worcester-Bosch 240) if fine for CH, but will only heat
DHW if the tap is fully on. If it isn't, or another tap in the house
is in use, the boiler will shut down.

Discretion being the better part of valour I bought a udder type mixer
shower just to check to see if it would work, and it won't. The boiler
just about fires up with the hot tap only on, but touch the cold tap
and the boiler shuts down.

Before I beg some expert advice;
- the diverter valve in the boiler was replaced a while ago
- the entire house water supply comes from a lead pipe(!) into a
single 15mm pipe.
- Cold flow rate is about 17 litres/minute
- Hot flow rate is about 8 litres/minute
- pressure is good, it's difficult to keep my thumb over the tap.

OK, I'm now begging. What is likely to be wrong and is there any way I
can fix it?
I'm looking for an excuse to replace the lead pipe (and the 15mm
copper), but most of the lead is the main side of the only stopcock.
Is this a plumber job or do I call the water company?

Now, assuming I'm up the creek here and have to go for an electric...
One particular member of the family will not have anything cheap
looking in the bathroom (pointing out that electric showers come in
very expensive and don't look much different seems to have no effect).
Is there any way I can avoid an annoying plastic box on the wall?

Thanks for your help!
-Andrew

BillV replied to Andrew Collins on 13 May 2004

That boiler should be just fine with a mixer shower that states its suitable
for use with combi boiler.
It seems that back pressure from the cold feed to the shower valve is going
into the boiler h/w output and so stopping the flow.
These valves often come with various restrictors that you put in either feed
to even out the flow.

Andrew Collins replied to BillV on 14 May 2004

Looks likely. I took the crappy Wilko udder thing apart and found a
rubber washer crammed in half blocking the shower head. Took that out
and put it in properly and hey presto, works.

Incidentally, I turned the DHW heat down a bit and the boiler seems to
fire up with less throughput. I would have thought this should be the
other way round... could be just an illusion, of course.

Thanks,
Andrew

Graeme replied to Andrew Collins on 14 May 2004

OT: your clock is a little fast, I think.

Andrew Collins replied to Graeme on 14 May 2004

Err, yes. A matter of some hours!

Cheers!

Andrew

Archived message: More mixer shower woes (UK D-I-Y House Improvement)