HW Tank Pressure Relief Valve occasionally dripping

This has just started tonight, water dripping from the overflow. Its the PRV at the top of the tank. I've felt the water via the tundish and its warm/hot, so I don't think it is the cold water PRV that shares the same tundish.

Watching the tundish this seems to 'spurt' slightly when the boiler and water/heating are on.

I changed the cold water PRV and reducing valve about 2-3 years ago, last one lasted 9 years. Cold water pressure vessel is reading just over 3 bar.

Hoping this is just the Hot water PRV, but shamefully has not been checked (by twisting the cap) for a few years. So is it normal for them to just go leaking ?

If your pressure is reading 3 bar that is fine.

PRV is at fault give it a good few twists to see if it will re-seat.

Otherwise replacement required.

Yes thanks, given both the hot and cold a good flush through. It didn't seem to work as it was weeping, but seems to have settled down so far so good. Otherwise off for a new valve tomorrow.

Just can't understand why it would discharge enough water to make the ground wet under the overflow for no apparent reason, then the valve was weeping ?

Thos is an unvented cylinder and they shopuld only be worked on by a qualified person.

The pressure you have mentioned is I think the AIR pressure in the expansion vessel. That is not necessarily the same as the water pressure.

But it may not be correctly charged.

My advice is to get someone qualified!

Tony