Hi. I'm having some issues with air in my system and I believe this should be an air release valve but I'm not sure how to operate it. It doesn't seem to push down or twist. Can anyone confirm what this is? I've attached 2 pics. This hot water tank is on the first floor, the boiler is beneath it on the ground floor, so this is a relatively high point in the system.
Many thanks in advance, Robin
Many thanks in advance, Robin