James Salisbury wrote:
"Doctor Evil" wrote in message
...

Lobster wrote:

I posted a query here a few months ago asking whether it was likely to
be worth my while biting the bullet and replacing the old incoming water
main with a modern wide-bore MDPE affair

Before digging the ground up, I would get the pipes inside right first.

1. Install a full bore stop cock.
2. Have a dedicated 22mm pipe directly to the unvented cylinder.
3. Tee off at the stop cock and run to all cold supplies in the house on a dedicated cold pipe.
4. Take the cold of the shower from the cylinder cold feed line, just before it enters the cylinder.

I've been looking at this again, and TBH the big problem is that I'd
just about have to rip the house apart to make all the changes you
suggest... eg must be about 17 metres from the stop cock to the HW tank;
that pipe is buried behind tiled boxing, under carpeted floors, goes up
and down levels, etc etc, all of which I'm sure contributes to the
pressure problem. I can't begin to imagine how much work it would take
to put it all right.

What it boils down to is, "is the problem severe enough to warrant all
that upheaval", and the answer has to be "no"!

If that sorts it then all is fine. If there is still problems replace the
mains pipe. Either way the internal pipes need sorting, so get them done
first.

One reason this issue has come now is that we're probably going to get
our drive done this summer, so now is the time to be digging it all up
to fit a new MDPE pipe out to the boundary. It certainly won't happen
after the new drive is laid.

So perversely, maybe it's the external pipework I'm looking at maybe
changing. Given the pressure readings in my last post, which seem to me
to indicate a 50:50 split between external and internal, would it still
be worthwhile changing only the outside pipework?

Check the isolation valves bewteen the pressure reduction valve and the
cylinder, sometimes these are not full bore, or are part turned off. Try
checking that that toilets and the cold side of the kitchen sink are not fed
from the pressure reduction valve. Check the strainer in the pressure
control valve is it furred up.

Lost me here... where would the pressure reduction valve be, and why
would I have one/need one, especially if I have a low pressure problem?

Thanks
David