PRV constantly going

[finchy01]

Before I just check another PRV in I just wanted to get any other thoughts.

Went to an invented cylinder the other day as PRV constantly flowing with hot water (not boiling). I repressurised the external vessel as this was totally flat and replaced the 2 ports as it had failed and stuck in open position but PRV was still going with inlet isolated albeit slower. I thought it may be backfilling from the kitchen mixer. Any other thoughts? (I am g3 before anyone starts worrying!)

 

[ShaunCorbs]

Once open they don't shut that good

Did you check pressure upstream to check reducing valve is ok

 

[Last Plumber]

Like shaun said, it may not have seated down correctly. After you've checked temps and pressure to rule them out, Change the valve !

 

[Best]

It is possible the sink mixer is backfilling from the mains to the hot. So check that out first, to rule it out.
This is something I have always said is a risk if the mains pressure at sink is uncontrolled, as is often done and deemed acceptable practice in homes with unvented units.
Although modern sink mixers do not in theory mix at spout if the tap has a fault inside the body it can pass from cold to hot and put the unvented unit at high pressure of whatever the mains coming into house is.

 

[finchy01]

Thanks for all the feedback guys. I checked pressure at tap but not with a gauge or anything. Surely 7 bar would be cracking the basin! I'm goino to go back with a PRV but will double check sink mixer too. Thanks again all.

 

[newcastle phill]

Expansion vessel too small ?