Caleffi is a decent make, I understand, but these fellows - well, the safety-release-valves - are prone to allowing a drip through after they've been activated. But thought best to change the whole thing, and now 6 months later dripping again, to my knowledge not been activated, so annoying faulty again after such short period? Since there are three 22mm pipes to hook up and the 15mm outflow you would probably otherwise need a 'union' to be able to make the connection to the tundish. I'm afraid I don't have much knowledge of these items - I do have a PRV fitted in my own home (and a Caleffi as it happens) but I'm not aware of it having a safety release valve on it. This multibloc is comprised of a pressure reducing valve, a pressure relief valve, and an internal check valve.

These Caleffi inlet control groups are designed to control the pressure on the mains supply of an unvented hot water cylinder. The item may be missing the original packaging or protective wrapping, or may be in the original packaging but not sealed. I'm struggling to think of anything that would cause the 'trapped' domestic side to increase like this.

It has been reconfigured from the original in that the 15mm outflow pipe is an easier connection due to it now being a swivel connector. li>