On Sunday, 6 December 2009 19:44:27 UTC, Vortex5 wrote:
Today I measured my incoming mains water pressure to be a little over 10
bar. About 145 PSI. About 100 metres "head"

Quite honestly I was surprised because instinctively I would have expected
it to be somewhat lower. What is normal though? Is 10 bar unusual?

It's never especially bothered me because I have an IMI pressure regulator
taking the in-house pressure down to about 3 bar....however the regulator
started playing up recently causing the in house static pressure to increase
a lot which could be quite alarming when filling a kettle.

The regulator is now fixed....and I am just curious.

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).