Dripping 3 bar pressure relief valve

[pwplumbing]

I am new to forums, but have a problem that I can't solve. First of all I am a qualified plumber including unvented systems. My 3bar pressure valve has been dripping for a few weeks now. I changed it for a new one thinking seal had gone or bit of crap has got stuck but the new one also drips. The expansion vessel is charged up to 2 bar and the system never goes above 2 bar when hot. It might be worth adding that the system uses an air source heat pump so hot is never above 60 degrees.

I have ruled out (but could be wrong) the filling loop as i would see the pressure rise or stay constant but it's dropping.

any ideas or could i be unlucky enough to get another dud valve? are some valve makes better than others?

Paul

 

[dontknowitall]

If you're sure the valve is dripping I'd buy another one.

Presumably it's not a leak? e.g. not enough ptfe in the joint?

 

[dancinplumba]

Why is exp vessel at 2bar ? 1 should be enough. Faulty pressure gauge ? Does prv drip when cold ?

 

[pwplumbing]

It's not a leak as it's going down the tundish. as this valve is only a week old I wanted to rule out anything silly on my part.

 

[pwplumbing]

I'll try dropping the pressure in vessel to see if it makes a difference. the prv does drip when cold I am thinking of replacing pressure gauge as well as valve.

 

[stevetheplumber]

are you sure that 3 bar is the right safety valve there usually higher than that on uvc although if the gauge doesnt hit three it must be a fault on either the gauge or valve with a new valve id try gauge first

 

[nowucit]

Try dropping the pressure completely then top back up slowly to the required pressure, at least then you will see at what point the PRV is passing and if the pressure gauge is working. If the pressure gauge is faulty it could be well over pressure already

 

[pwplumbing]

It seams to have stopped now that I have dropped the pressure in the vessel (although it had work for years at that pressure) I'll give it a week and if it's still dripping I'll change both valve and gauge. I don't really want to release pressure more than I have to, antifreeze is expensive.

 

[pwplumbing]

3 bar is correct for central heating circuit, the unvented cylinder has a 6 bar prv and 10 temp/prv

 

[pwplumbing]

OK, confession time. All off my prv's share the same tundish. I pulled apart the pipe from the central heating prv and it was wet so I came to the conclusion that it was that that was the problem I have just been in to the cupboard and caught the system dripping heavier which coincided with the hot water heating time. so tested the vessel for the hot water and it was empty of air (don't know why) I've pumped it up and i'll see how it goes.

Thanks for all you input but you were dealing with a muppet.

Paul