Mains Water Pressure. What is "typical"?

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.

Reply to
Vortex5
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That's high.

Normal is around 3-4 bar, but I've seen as high as 7. I've never seen 10.

Reply to
Ron Lowe

I'd expect 2-4 bar.

Bob

Reply to
Bob Minchin

Ron Lowe wibbled on Sunday 06 December 2009 19:46

Yes. 4+/- bar is quite common. Mine is 7.5bar, limited to 5 bar by regulator. 7.5 bar is pretty crazy - couldn't imagine what 10 would be like.

Without a regulator, that would be right at the limit for a lot of equipment.

Reply to
Tim W

Good grief, that's at the limit of my air compressor. Your plumbing must be made of extra-thick steel pipe.... :o)

Reply to
Steve Walker

Some years ago I recall measuring the pressure at about 8 bar, but have lost the pressure gauge.

This measurement was taken with a brand new "monument tools" gauge I purchased recently.

I originally installed the regulator after fitting a segment of Hep2O internally and was uncomfortable about such high pressures with plastic (incidentally Hep2O is rated to at least 12 Bar safe pressure at room temp so I was being paranoid).

I'm going to borrow another pressure gauge just to be sure I don't have dodgy equipment! Will also call the waterco to see what they have to say.

Reply to
Vortex5

They'll tell you to turn the pressure down by partially closing the stoptap, which is what you should have done before buying a regulator.

Reply to
Phil L

My guess is "3-ish"

I got a bit concerned about some work I was doing, 'phoned our water provider and asked. We'll check they said. I awaited their call. Meanwhile I asked No 1 son, Civil Engineer in water elsewhere in UK answered, "Don't be daft, most are about 3bar + or -. " Then our Co called back... The Chief Engineer of the water Co. where I live called back. He replied it's about 3.5-4 when it leaves our header where you live, so based on your postcode, 3 bar would be a good number!

Ho Hum EP

Reply to
ephraim_pule

Why on earth would they say that? It won't make any difference to the static pressure.

....or is there a pressure regulator at the exterior stop tap tap? (I find that hard to believe)

Reply to
Vortex5

Phil L formulated the question :

Partially closing the stop tap, will not affect the pressure, except when there is flow. The static pressure will remain the same as before.

Reply to
Harry Bloomfield

So even when the tap's just trickling, the water's at 10 bar?

what if it's turned down so low that it's just a slow drip when fully open, is it still at 10 bar then?

Reply to
Phil L

Just another thought: Turning the supply valve or tap down isn't really a solution if the pressure is as high as you suggest. Clamping down a valve may reduce the flow but it won't change the pressure. When the flow stabilises, the pressure will be the same. It's a bit like volts and amps. "Volts is pressure, Amps is flow"

Please no flames...... the OT has a pressure (volts) problem not a flow (amps) problem so squeezing the flow won't help.

I remain curious about the pressure/head being reported in the original post. I suspect that most providers in UK don't supply water much above 3, 4 or 5 bar.

EP

Reply to
ephraim_pule

When the internal tap is off, yes.

Reply to
Vortex5

Yes but it wouldn't stay at that pressure for more than a second or two when using a tap, so filling a kettle, as you mentioned in your OP, wouldn't be 'alarming'

Reply to
Phil L

What really confuses me is that there are plenty of houses around me on higher land, none are more than about 20 metres ( - 2 bars) higher.

I could understand if pressure was (say) 5 bar, but cannot understand why I see 10. hence the original post.

As I said previously first stop is to double-check the instrument. I'm wondering if I can bodge up a connection to do this pneumatically at the local garage.

Reply to
Vortex5

Correct.

That's the typical range.

Water co's do play about with pressure, if works are undertaken they drop it down noticeably, then ramp it back up once complete. The problem with 10 bar is water hammer (flexible w/machine hoses) is going to get brutal on the pipework.

Reply to
js.b1

Phil L wibbled on Sunday 06 December 2009 21:53

Reply to
Tim W

Phil L wibbled on Sunday 06 December 2009 22:27

I beg to differ...

That's not a reliable method of regulating dynamic pressure, which will now be all over the place depending on demand.

It also doesn't help any equipment that doesn't like such high pressures as they will be seeing the static pressure regularly. It would also be a potential disaster if the OP had mains pressure DHW and plastic.

Looking at an offcut of JG Speedfit pipe, I see the pressure ratings are:

12bar at 20C 4 bar at 82C 3 bar at 92C

The figure for 60C isn't given but I can't see JG pipe enjoying 10bar at much over 40C if that.

IME, certain garden hoses (hello Screwfix) fail early at 7.5bar, so for anyone with 10bar static pressure, I would rate it as a *very good* idea to include a pressure regulator next to the stopcock. I found 7.5 bar a big enough pain to include a regulator in my system. No real disadvantages and a decent device does not reduce the flow (I tested this specifically). CAme in very handy when I wanted to install a water heater that required

Reply to
Tim W

Note the mention of the words 'static pressure' by Vortex5. The word static means in this case, no water flowing.

Reply to
Harry Bloomfield

ephraim snipped-for-privacy@hotmail.com explained :

The word you are looking for is 'resistance' in the electrical sense.

A restriction to the flow of water could also be called resistance to flow.

Reply to
Harry Bloomfield

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