So I did already google what to do about this - turn off water. drain all water from lowest point in building. turn back on water slowly to allow air into the pipes - but it hasn't worked at all. The banging only started recently after a plumber turned off our water to fix our toilet. From the moment he turned it back on there has been banging. And not just when someone uses water in the house by a tap/washing machine etc. It's constant. What the hell can I do because it is driving me crazy?!