Although it looks a bit ‘wimpy’ this little flow restrictor seems to have solved my water hammer problem. I used the 2 litres/min restrictor in conjunction with a small pressure tank (which did not work on its own) in the main feed up to our cold-water tank. I reasoned that in an electrical circuit you use a capacitor and a resister to smooth the voltage. Due to the severity of our water hammer (it was enough to shake our banisters) I fitted the restrictor up by the ballcock where it would do least damage if it broke loose. The instructions did not seem to say ‘shorten the copper pipe just a little beyond the olive to make room for the restrictor’ which is required but otherwise all was fine. Over the last couple of weeks or so we have had no water hammer or problems of any sort. 2 litres/min may seem a small flow but the cold-water tank again smooths out our need.