On 3 Oct 2006 05:27:48 -0700 someone who may be "Spat"
wrote this:-

more gravity fed shower fitting questions! [snip]

Also, I'm planning to branch off existing bathroom pipework, the
instructions for a mira realm says cold must come from a cistern, I'm
not sure if the cold is from mains or not, is that likely,

It depends on which part of which country the house is in and the
age of the plumbing. Perhaps 50/50 over the whole of the UK.

or even something to worry about?

It is very much something to worry about. Imagine the situation
where someone is showering under a non-thermostatic shower when the
mains water fails for some reason, but the gravity fed hot water
continues for some time. They are likely to be scalded, perhaps
killed.

It's certainly at higher pressure than the hot water.

Then it is highly likely to be from the mains. Follow the
instructions, someone went to the trouble of writing them for a
number of reasons including your safety.

If the shower is thermostatic and you wish to trust your safety to a
mechanical gadget, rather than doing the plumbing properly, then a
pressure equalising valve can be fitted to make the thermostatic
valve work somewhat better.


--
David Hansen, Edinburgh
I will *always* explain revoked encryption keys, unless RIP prevents me
http://www.opsi.gov.uk/acts/acts2000/00023--e.htm#54