I have a Vaillant Thermocompact which has reduced to 0 Bar pressure. Whenever it starts up there is a banging sound for a few minutes, but this dies away and it does actually work for both heating and hot water, but the noise is clearly not right and I think associated with the zero pressure. I only have the unhelpful advice from the manual about consulting the non existent installer's instructions about how to fill the sysytem. I have looked at the nearest current equivalent manual for the ecoTec Pro which talks about opening the valve on one of the 4 pipes underneath the bolier to let in water. Unfortunately, my boiler only has 3 pipes leading to it. The middle one is the gas pipe and the outer 2 are water, but all 3 already have their vales in the open position. At the far right is a 3 bar pressure relief valve. I think my system refil must be somewhere else, but where do I look for it and what does it look like? I have a utility cupboard that houses the enormous hot water tank with a smaller pressure vessel above it and a mass of piepwork and lever valves that interconnect all this (including a water softener and a large pressure pump to provide high pressure water to all our taps) - it's more complex than the Tornado I fly for a living! So before I do somethging terminal and twiddle the wrong valve, and before I resort to a plumber, can anybody suggest how I might refill the system to get pressure back in to my boiler.