Hi, my boiler pressure is showing as just above zero. It will take weeks to get an engineer as it is on housing association contract. I know the system needs topping up, but haven't a clue how to do it, and manual has no diagrams which I can recognise. I'm sure I can do this myself, but I don't know what to look for.

Under the boiler is a panel, and within that is a smaller panel. I took off the smaller panel which exposes two pipes. One on the left has a flat black switch.

The larger panel is nicely finsihed off around the edges so I don;t want to disturb that one until I have an idea what to do.

Can you help?