Pressure Reducing Valve

[nitro23456]

Hi all

I have the pictured PRV on my incoming mains. It has always read about 4bar where the red indicator is, but I have noticed it creeping up to 6.

Is this something to worry about? Hot weather related perhaps or is it knackered?
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[Johntheo5]

Run off a few liters of cold water and see what the static pressure is when you reclose the tap, then watch it for say 15 mins or so with no water draw off and see what it rises to.

 

[nitro23456]

The pressure dropped to about 3 with the tap open, then rose to just over 4 when I closed it and then has risen back to nearly 6 over a period of time.

 

[jeff the gasman]

Cold water coming into a warm space will expand and raise the pressure.
There’s no way to expand back to the service pipe.

 

[Johntheo5]

The pressure dropped to about 3 with the tap open, then rose to just over 4 when I closed it and then has risen back to nearly 6 over a period of time.

If you have a drop tight PRV then pressure rise possible as the water is trapped between the PRV and the cold users but still unlikely IMO to cause the above rise, other possibility is that the PRV isn't now or never was drop tight and a new meter with NRV has been installed recently at the mains end.
Maybe just shut the stopcock, reduce pressure to 2 to 4 bar, if holding tight, pressure IMO should not rise.

 

[nitro23456]

Is the current pressure of nearly 6 going to be an issue though?

I cant tell any difference at the taps tbh.

No new meter installed.

 

[Johntheo5]

No, shouldn't be a issue as the pressure falls and is controlled to 4bar? once a liter or two is run off, it would only be a issue if this PRV is also used to supply cold water to a unvented HW cylinder which hasn't got its own PRV (combination valve).

 

[nitro23456]

This has crept up to above 6 bar now at rest.

Is that the incoming mains pressure before the valve rather than downstream pressure that is feeding my appliances?

When I turn on a tap it drops to around 3 bar, so that is the pressure the PRV is controlling the downstream to?

 

[Johntheo5]

With running tap(s), 3bar pressure would be the PRV setpoint pressure, the mains pressure, upstream of the PRV, will fall somewhat due to pipe friction losses but the PRV will/should maintain this downstream pressure very close to 3bar. When you close your tap the PRV should still maintain your 3bar pressure despite the upstream mains pressure returning to 6bar or whatever.
If the PRV is leaking past it's seat even by a very tiny amount then the downstream pressure will rise eventually to the upstream pressure, 6bar your case.