I’ve got a slow loss of pressure in my sealed system, cant see any obvious leaks, but its been suggested it could be the expansion vessel, so i should pressurize the system then open + close the release valve a few times to make sure no debris jamming the valve, and also to check the air pressure in the expansion vessel.

What pressure do you set this to, do i just match the cold system water pressure, which is currently 1 bar for our bungalow?

Stick a sandwich bag over the discharge pipe and hold it in place with a spring open clothes peg. If its discharging, you’ll end up with a bag full of water. You can add a fake goldfish to the bag for added comedy value.

Depends on your boiler, but about 10psi is about right for mine.

I tried it a few times before I actually did it right. Just pumping up the vessel to the right pressure didn’t really work.

Open drain valve next to boiler, let it drain away to zero pressure, close valve, pump up to 10psi, open drain valve, more water will possibly come out + expansion vessel pressure may fall, close valve, pump back up to 10psi, repeat until no more water comes out when you open valve, then repressurise system to just over 1 bar.

Working perfectly now.

does depend on your boiler – helping a mate at the weekend whos vessel seems to be failing and manual said 1 bar. was an RD628 boiler He was getting system pressure going to 3 bar then dumping and locking the ignition system out. Over the course of a week his vessels leaking out the pressure. So a plumbers been commisioned to fit a new one – as like many modern cars the expansion vessels in a position where its not easy to remove so im not getting involved in that

my grant needs 1 bar an all in the expanison vessel – and 1.5 bar COLD system pressure

so instead of asking us generally what pressure it needs – get the manual out 😉 – if you dont have one google the make and model and find one. really handy things to have