Some help would be appreciated. I`m fitting a new basin, wc, and bath. The cold water supply was easy to isolate however the hot water supply to the basin and bath seems a bit tricky. There are no service valves or any other valves between the cylinder and bathroom. The supply runs from the top of the water cylinder. I have turned off the boiler. Would I need to drain the complete water cylinder to stop the hot water supply to the bathroom? thx for your help?