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Prv raise

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Just had a pressure reducing valve fitted above the stop cock about 3 hours ago to reduce high static pressure that I had, it was set at 3 bar static and sat on 3 bar after the plumber ran taps etc…. I’ve just noticed that it’s now reading 3.5 bar static is this normal for it to raise slightly?
 
If they haven't installed a drop tight PRV then yes they can suffer from creep. TBH if you have 7bar static then you don't want a PRV that suffers from creep, as was suggested.

 
The prv they installed was Honeywell D04FM, not sure if it’s a decent one or not?
 
If they haven't installed a drop tight PRV then yes they can suffer from creep. TBH if you have 7bar static then you don't want a PRV that suffers from creep, as was suggested.

The prv they installed was Honeywell D04FM, not sure if it’s a decent one or not?
 
It's not a bad valve but it's not drop tight. They could have installed a Reliance Predator 312 for less money, especially if they got their valve from SF as the Reliance is available from the same place and that is drop tight, would just need to add a gauge
 
It's not a bad valve but it's not drop tight. They could have installed a Reliance Predator 312 for less money, especially if they got their valve from SF as the Reliance is available from the same place and that is drop tight, would just need to add a gauge
Bloody hell so does that mean I’m just going to have the same issue as before then?
 
All really down to how much creep the valve allows and that usually dictated by how much static pressure there is. That's why I suggested to ask for a drop tight valve.

All you can do now really is keep an eye on it and see how much it rises overnight.
 
All really down to how much creep the valve allows and that usually dictated by how much static pressure there is. That's why I suggested to ask for a drop tight valve.

All you can do now really is keep an eye on it and see how much it rises overnight.
Okay thank you! When I contacted our housing repairs team I did mention about a drop tight prv, guess they just ignored that part.
 
Well the one they installed isn't drop tight. Unfortunately it wouldn't surprise me if the installer didn't know what a drop tight PRV is.

If it's a HA can't you ask them to come back and swap it out for a drop tight valve?
 
Well the one they installed isn't drop tight. Unfortunately it wouldn't surprise me if the installer didn't know what a drop tight PRV is.

If it's a HA can't you ask them to come back and swap it out for a drop tight valve?
Yeah it’s a HA I’ve asked them, they said they are going to pass it onto the supervisor to speak to me about it. If they say no I’ll just pay a plumber to sort it properly, rather that than a flood lol
 
From my Archives

Drop Tight PRVs

Caleffi 535

Reliance 312 Series

Honeywell D05

Honeywell D06

NON Drop Tight PRVs

Caleffi 533

Reliance Predator (PRED800015)

Honeywell D04
 
Well the one they installed isn't drop tight. Unfortunately it wouldn't surprise me if the installer didn't know what a drop tight PRV is.

If it's a HA can't you ask them to come back and swap it out for a drop tight valve?
Just noticed when the boiler does its pre heat or hot water is used that’s when the static pressure goes up on this gauge, even though I don’t have a water tank it’s all on demand water heating?
 
The PRV acts like a non return valve so the expanded water rises the pressure, some/most combi manufacturers now specify a small expansion vessel on the cold mains at the boiler due to failing plate heat exchangers and don't think they are covered under warranty unless the EV is installed.
 
The PRV acts like a non return valve so the expanded water rises the pressure, some/most combi manufacturers now specify a small expansion vessel on the cold mains at the boiler due to failing plate heat exchangers and don't think they are covered under warranty unless the EV is installed.
What would you suggest I say to the plumber? Our boiler is a Worcester mt10, fed from the mains, no water tank in loft or cylinder, prv at stop tap was only fitted today, would you suggest a expansion vessel because of the prv
 
I suppose, ideally, yes, especially with a preheat combi but suggest you keep a eye on it for a day or two, I think the boiler heat exchanger is OK up to 10bar, but there are always some traces of air in the system which will probably absorb the pressure, you're probably only talking about 50ml, 0.05L or less of expanded water after preheat. What you might consider is running a hot tap for say 5 minutes with the boiler switched off, then shut the tap, note the static pressure, switch the boiler back on + preheat enabled and see what does the ststic pressure rise to then?.
You could also, sometime, do that test but let the boiler + preheat off for say 30 minutes or so and that will tell you the true rise in pressure due to the PRV (creep) leak past.
 

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