Knocking pipes?
 

Hi All

The hot water tap in our downstairs loo has been recently replaced by one of
those quarter turn jobbies. Now it is noticeable that, when you turn the tap
off quickly (something that we couldn't do with the multiple turn taps),
then there is a banging pipe sound; just for a second. The hot water comes
from an upstairs cylinder fed from a loft header tank.
Anyone got any suggestions for a remedy? Ta.