Topping up pressure on i35 combi boiler

chd87

Hello, I need some help with low pressure on my combi boiler. I haven't needed to top up pressure on the boiler since we moved house but checked today and pressure is low. We have an i35 combi boiler. From what I have read there should be 2 blue taps for a filling loop, my boiler only has 1. The blue tap does not do anything on its own. But slightly further down the wall there is another black tap that looks to connect to the same pipe - is this the filling loop? I don't want to mess around with taps as being able to top up the boiler is probably the limit of my ability!

hot_rod

Blue should be for the inlet cold water, red is the hot output these are for the domestic hot water on a combi boiler , typically. The hydronic, heating valves are not usually the colored valves. The boiler manual should indicate the connections