"Ian Stirling" wrote in message
...
Lobster wrote:
Ian Stirling wrote:
Lobster wrote:

Hi all

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, specifically to prevent my
shower pressure from being so badly affected by other water outlets in
the house (it's all fully mains pressure, with an unvented HW system).
I was advised that the best course of action was to take some water
pressure measurements close to the stopcock, which should help diagnose
the location of the pressure drop (see original thread below

snip

Here's some data:

a) Static pressure, no water flowing: 3.9 bar
(Flow rate measured at kitchen sink, no other water running: 20 L/min)

b) Shower running (nothing else): 3.8 bar

c) Shower running, plus bathroom sink tap and toilet flushing - causes
severe reduction in shower flow rate: 2.7 bar

d) Every tap/shower in the house running - causes shower to stop
completely: 1.8 bar


Right.
So, (approximately) if you were to cut the pipe immediately after the
stopcock, it'd read 0 bar.
With every tap/... in the house running, about half the pressure loss
is in
the inlet, half in the house.
Increasing the bore of the pipes in the house, and the taps will
significantly
increase your flow.

Thanks. So are you saying that you reckon increasing the bore of the
pipes inside the house would have the same effect as renewing the
incoming pipe, and that presumably these effects would be additive?
Neither would be very easily accomplished, all the same, mainly due to
the geometry of the house. It's the shower that's the issue, so which
pipes should I be looking at inside: between HW cylinder and shower?
Stopcock and HW cylinder? Stopcock and shower? All the above?(!)

Is the house one or two stories?

Two.

Ok.
Part of the problem is that it's two stories, the shower will see at best
0.4 bar less than a tap in the lower story.

Does the heating come

He said he had an unvented cylinder.

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.

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.








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