Shower/mixer Tap

[retrocop]

Any Plumbers out there.
A recent problem has cropped up with the shower mixer tap in the downstairs bathroom. The cold is fed by direct mains pressure and the hot by gravity feed from the hot water tank upstairs.This system has always provided a good powerful shower because of the "head".When the mixer diverter knob is pulled up to shower mode the hot and cold will not mix to a satisfactory temperature no matter how much balancing is attempted on the two taps.It is either hot or cold.When the diverter is depressed(If it has any relevance to the problem it is very stiff) to bath mode the hot and cold water will mix to a suitable temperature.
It is not a very expensive mixer tap and about 10years old.Does anyone know of a simple solution or is it a renewal job? Advice appreciated.Thank you.

[bhg481]

I was under the impression that it was not legal for a mixer-shower to be fed directly from the mains - if someone turns on another cold tap whilst you are in the shower there is a risk of scalding as the cold-pressure to the shower will drop.

[retrocop]

bhg
Yes we are all aware of that in our family for the last 35years we have lived here.It is a given in our family that no one flushes the toilet next door whilst the shower is used otherwise a lot of expletives are heard.Visitors are also warned.We are happy with this system and used to it.I do not want to have extra pipework from the cold water tank to the cold water feeds.
This house was built in the 1920's and it was not illegal,I understand,to use this method unlike today in modern housing.

[The Builder]

As I'm sure you've discovered, retro, it's a bit fiddly combining mains and gravity feeds. It wouldn't take much of an obstruction to mess things up.

The diverter is stiff. That suggests a partial bung-up inside the mixer body. It's usually a fairly simple job to dismantle the mixer and clear it out. It may well be hard water scale.

Clean, and re-assemble with new O-rings if there are any.

[retrocop]

The Builder
Thanks for your advice.I was hoping and relying on you to answer my post.You didn't let me down.I will see if my local plumber can dismantle and clean it out.I would of done it myself once in my younger days.In fact I put the mixer on the bath myself but find it physically impossible nowadays.:-(
Thanks once again.

[Sipowicz]

Does the bathroom have a Lou?

[retrocop]

Sip
No it is a separate Lou unlike the other Lou which is segregated. :-(