Pressure Reducing Valve

[Paulhar]

Hi All,
I've recently installed an unvented Andrews 270 litre gas-fired water heater in a ten-flat hmo and to reduce the chance of leaks I put in a pressure reducing valve. I went for the drop-tight design which is supposed to limit the pressure under no-flow conditions . . . except it doesn't. The pressure gradually creeps up when no hot water is being used. I've tried two different valves, both behave the same. There is an expansion vessel after the valve so it's not down to temperature rise. Any ideas gratefully received.

 

[John.g]

Have you confirmed it by isolating the mains?, or any possibility that its being pressurized back through the hot side from a mixing valve.

Don't know what makes of PRV you have tried but...
The Caleffi 533841H doesn't specifically state that it is drop tight but I confirmed with Caleffi that it is , in fact, drop tight.
The Honeywell D04 is not stated in their brochure as being Drop Tight whereas their D05 is stated as being Drop Tight,

 

[Paulhar]

Tha ks for the reply. The valve I'm using is this one which I thought was drop-tight.

Predator Pressure Reducing Valve

Reliance Valves Predator Pressure Reducing Valve for hot and cold water applications.

www.rwc.co.uk

I hadn't considered back pressure from a mixer, I'll put a non-return valve on the hot outlet just in case

 

[Piyush Patel]

The name already gives us hints. The Pressure Reducing Valves are used when the pressure of water is on the higher side like more than 50 PSI then the valves help in reducing the pressure.