On 05/04/2019 10:09, Andrew Gabriel wrote:
On 04/04/2019 18:41, wrote:

The water companies have a statutory minimum pressure they have to
deliver. They should also have a statutory maximum of 4 bars. 4.5 is
the rated working limit for many central heating boilers etc. Above
that will damage them. A fitting blew off the mains supply in my
mothers flat at somewhere between 7 and 11 bars. Three flats
uninhabitable for 18 months and £200k insurance bill. No liability to
the water company. Partially closing the main supply valve reduces
flow, (and make noise) but does nothing to reduce pressure. You need a
reducer on the system if it is above 4 bars. The big step down valves
on the water mains they install now are not fail safe and have a habit
of failing by giving full pressure - 11 bars etc. Not good for your
system. The design rating of copper pipe is 12 bars but the fittings
etc are your weak point. If your system is going to see over 4 bars it
needs to be properly pressure tested and certified to take max
pressure + 20%. This countries standards are so bad it makes me weep,
(my pipework as well).


4 bar is for the sealed system. Mains pressure can be higher than that.

A pressure regulator only really works with a flow through it.

Not so.

The
static pressure (when no flow) will always be higher than the set point
(although not necessarily the fill input pressure - that depends on the
volume of pipework downstream). The downstream plumbing must be able to
handle the static pressure, not just the regulators set point pressure.

That is just plain WRONG.

For example as I found out recently my mains pressure HW cylinder has a
regulator on the input. When the pressure rises above 2.1 bar it shuts
off flow into the tank completely. There is an air bubble pressure
maintainer so that there is 'elasticity' in the system.

The valve on your loo shuts off input completely. That does not mean the
cistern is at 10 bar!

You are thinking of flow reduction as a means to achieve pressure
reduction. Then what you say applies, but that is not what a proper
pressure reducer does.

--
"Strange as it seems, no amount of learning can cure stupidity, and
higher education positively fortifies it."

- Stephen Vizinczey