I live in a Bungalow and I have just drained my heating system, cleaned and refilled including some inhibitor. I think I have bled everything properly, but I think I have an air lock. I now have banging pipes which sounds like it is coming from the feed pipe, with hot water going back in to the header tank. This happens when the heating or hot water is fired up. I do not seem to have a vent pipe going back in to the header tank, (see pic 1). Would adding a vent pipe as in pic 2 solve the problem? If so, what height should it be above the tank, and does it look like it is in the right place? Any advice would be greatly appreciated.