hot water pipes?

when we use the hot water pipe in downstairs loo, the pipe sounds like its banging or similar. This can be started by kitchen tap and upstairs tap also. BUT only stopped in loo downstairs, after turning hot water tap on and then turning off extremely slowly. Noise dose not always stop when hot tap has been turned on. takes a little time. (until my head has been bashed against wall) ! :)

EMMA
March 2011