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Andrew Gabriel

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. 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.

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Andrew