"Christian McArdle" wrote in message
et...
A twin impellor pump pressurises both hot and cold gravity supplies. A
single impellor pump can either pump a single hot water supply (as you are
using mains cold, which needs no pumping) or can pump the outlet of a
flush
mixer valve before it gets to the hose/head.

Well, we currently don't use mains cold, but as it goes to the basin I
presume it wouldn't be too difficult a job to branch it off to the
bath/shower too.

Provided you have a cylinder thermostat with a large hysteresis, the
primary
circuit will not be hot for long periods of the day. You will easily still
save money over an electric shower in energy efficiency. Also, it
shouldn't
be difficult to lift a couple of floorboards and stick a thin layer of
insulation on the pipes if the heat bothers you.

Isn't the idea of an electric shower that it saves money by only heating up
what you need? I think the powerful ones are about 10.5kW ... does that
sound right?

Leaving it running all day I think would be wasteful as I'm only
awake/there for about 7 hours a day!

Then time it to run from 1 hour before you are there/awake until 1 hour
after. You should never run out then.

I do and I currently don't (run out that is!). It's enough for 4 people in
the course of an hour to all have hot water. My only experience of a power
shower is at the in-laws, where it sucks the hot tank dry in about 10-15mins
.... which is crap!



a