Hi guys, wondering if you could help. Our boiler pressure is at about 0.5/0.4 and is in need off topping up. Problem is I can't figure out how to top it up. Now about 3 years ago when we moved in the system was fully drained and I refilled then but for the life of me now I can't remember how I filled it. There's a filling loop which isn't in your typical location it's on some pipework much further down. So the the cold feed goes up and has an isolation valve from this the filling loop is connected. This travels up to a pipe on the left and looks like it feeds into a one way check valve (think this is correct name). So I opened up the isolation valve and nothing. So I think is it either a blocked isolation valve or is the check valve faulty. Or am I missing something really simple. Cheers for any help