That pressure relief valve was leaking on my heating , i waited until it was due a service to get it fixed. My plumber/cowboy didn't have one so he removed it, blanked the pipe off and came to replace it about six months later ,saying that if the pressure built up too much it would end up in the overflow tank,

I don't get that. Depends what he meant by overlfow tank. But it makes me think of the overflow you can get when minimal pressure builds up in a vented system, driving the water back up (defeating gravity) for it to drain into a tank., it's because you have a vented circuit which feeds excessive water into an overflow tank. But if you have a vented system you wouldn't need a PRV in the first place :confused:

I don't get that. Depends what he meant by overlfow tank. But it makes me think of the overflow you can get when minimal pressure builds up in a vented system, driving the water back up (defeating gravity) for it to drain into a tank., it's because you have a vented circuit which feeds excessive water into an overflow tank. But if you have a vented system you wouldn't need a PRV in the first place :confused:

Thanks for that ,i do have a vented system like you described,as when the thermastat failed last year the hot water was going up into the tank.The guy who fitted it must have been a belt and braces chap.

The Stanley Range that heats my water etc insists in the instructions that it has a prv fitted within a certain distance of the boiler however its plumbed - sealed or open, perhaps in case you get a blocked pipe? My problem was I've never seen one like that before.