Mains static pressure off the scale!!

[Barnjules]

Hi everyone,
I'm new here and would love some advice regarding my mains connection.

I'm near completing my barn conversion, and this morning filled up my system (thermal store,rads,ufh etc)with the help of my plumber(who is now gone and unavailable to ask for advice!). I fitted a new prv just after the internal stopcock as our pressure is very high here. When a tap is turned on (and whilst we were filling the thermal store),all was good,as the prv maintained the dynamic pressure at 2.5 - 3 bar. However, after plumber has left,and things were just sitting, i.e.,no taps etc on, i noticed the pressure guage on the prv was off the scale (over 10 bar). I understand this to be reading the static or standing pressure. This seems super high to me, with all taps,fittings etc that are under mains pressure having to withstand this.( i dont even know the true reading,as the gauge only goes to 10 bar,and the needle's off the scale!)

As the water supplier (southwest water) say,they have no obligation to maintain a maximum pressure, can i get a prv that reduces static or standing pressure, or is 10 bar+ normal ?? (I'm sure it's not!)

Very frustrating,and I've closed the stopcock for now..just in case : (

Any advice greatly appreciated.

Thanks,

Jules

 

[Stigster]

I don't know what types of fittings, pipework and fixtures you have in the house but as far as pipework and fittings go, 16bar on the cold seems to be a common figure for what they can reliably withstand. Outlets and fixtures is a refer to manufacturer's instructions deal usually.

As for the pressure reducing valve, the pressure reading that you see when the system is static will be the pressure on the incoming side of the valve. They usually operate on a spring loaded washer which is closed when no outlets are open. Therefore the pressure on the outlet side will not increase past the set point on the valve. Only when an outlet is opened will the water be able to flow, pushing open the spring loaded washer and only to the pressure set on the valve.

So, with a functioning PRV on the mains, your pipework and fittings will not ever get to feel this 10 bar+ pressure.

 

[Barnjules]

Thanks stigster for your quick reply. (I just typed a reply to u but the dam system seemed to have lost it..so here goes again)

You've put my mind at rest ...to a point! Out of interest,i looked on a suppliers site who ive used for most of my plumbing stuff, and they DO do a prv (for 'commercial use') that says it regulates dynamic AND static pressure,where other types only state dealing with dynamic pressure. So, i dont know what the difference is,given what you said..that my fixtures,outlets etc would never feel the 10+ bar showing on the guage when things are static.

However, i still feel a little uneasy sleeping soundly in my static caravan leaving the stopcock on overnight!

Another thing is that earlier today, my plumber wanted more pressure to fill the system, so i cranked up an old external prv (which i fitted years ago when we first got the place). He reckoned it was knackered, so i quickly removed it from the blue alkathene, only to find that his filling problem was due to an airlock somewhere! Now we have super high pressure in the caravan and i wad wondering if it was okay to re-fit it (or a new one), which will effectivley give me two in line prv's for the supply to the barn. Does this sound okay?

Any more thoughts or advice would be greatly appreciated!

Cheers, Jules

 

[Best]

This has interested me because I always thought the gauge on a PRV showed the pressure from after the valve and therefore usually 3bar for most types, which will obviously fall on taps opening and only ever rise a little on heated supplies, like unvented units

 

[Staffy85]

This has interested me because I always thought the gauge on a PRV showed the pressure from after the valve and therefore usually 3bar for most types,

yea same here, probably depends on the brand of valve fitted? , I thought same as you though , it would make sense too for confirmation of pressure being reduced.. Barnjules if you have any doubt you can buy test pressure gauges for this which can be fitted a number of different ways ROTHENBERGER Water pressure gage 0 - 10 bar - vat receipt | eBay cheaper ones out there,

 

[SimonG]

Always need to set the prv with water running.

 

[ShaunCorbs]

you put the prv the right way round?

 

[mfgs]

Interesting, I assumed them stopped the pressure increasing after the valve be it static or dynamic. You could put it to the test by installing a pressure gauge on the pipework after the pressure reducing valve.

 

[SimonG]

The gauge on the prv is after the gubbins.

 

[mfgs]

Then do they reduce static pressure or just dynamic?