Source for 8-bar water pressure-relief valve

[Caecilius]

Following on from the "What's this dripping pipe" thread a couple of weeks ago...

I've got a weeping 8-bar pressure relief valve on the cold water inlet to a megaflow hot water cylinder, and I want to find a replacement.

The prv looks like this:

So it's got 22mm copper input and output pipes, and a 15mm copper drain pipe with compression fittings.

I'm pretty sure the prv is faulty, as my mains water pressure is only about 3-bar at the garden tap, and this thing is on the first floor and downstream of a 3-bar pressure reducing valve. I've tried manually operating it and letting it spring back in the hope that it will re-seat but to no avail.

Any ideas where I can find one of these things? I've had a look in the toolstation catalogue but can't see one there. An online search isn't throwing up loads of hits.

I'd like something that would be a drop-in replacement so I don't need to alter the pipework.

[Bob Minchin]

Can you live with 6bar? They are common for solar thermal systems

[Bob Minchin]

Looks like it could be a combined temperature and pressure relief valve

- might have to be a genuine mega(bucks)flow part.

[newshound]

Assume you have tried BES? ISTR they have a reasonable range

[fred]

In article , Caecilius writes

RWC appears to relate to Reliance Water Controls but they appear to be a bit cagey about replacement parts for mains pressure DHW systems.

Searching for RWC pressure relief valve "8 bar" brings up an option for a replacement cartridge that may work for you:

From other info is appears there is another service kit that includes a replacement seat and that may be the one you need as the seat may be damaged.

Have you turned off, depressurised and opened the knurled cap to see what's inside? You may find it is just the calibrated cartridge and the seat at the base which may just need a clean up.

[Caecilius]

Yes, the pressure shouldn't rise above 3 bar anyway. I'll take a look at six-bar ones. Thanks for the pointer.

[Caecilius]

I guess it could be, but it doesn't need to be because it's on the cold water inlet side, not the hot water outlet.

[Caecilius]

Ahh, that's interesting. Yes, it could well be the cartridge and seat. The prv is only a couple of years old anyway, so I doubt that there's anything wrong with the brass bits.

That twelve quid cartridge may be worth a punt if it's not just the seat, so thanks for that link.

[Roger Mills]

Are there any reference/type numbers on it anywhere, besides those visible in your photo? If so, Google - using them as a search key. I needed a new pressure + temperature relief valve for my unvented hot water cylinder, and managed to find a suitable alternative on Ebay.

[Tim+]

How certain are you that the valve isn't working correctly? If your cylinder has lost it's air bubble then cylinder pressures could be rising too high.

Have a look at this.

[Tim+]

Fecking auto-correct! I typed "its"!! ;-)

[Caecilius]

I should have mentioned that I'd already been through the megaflow regenerate air-gap process. But thanks for mentioning it, as it could have been the problem.

The PRV continues leaking after turning off the boiler and drawing off some hot water. So I'm pretty sure it's the prv at fault.

[Stephen]

The letters RWC gives the manufacturer name, Reliance Water Controls..... Google is your friend... :-)

[Caecilius]

Thanks, I think I've found it: