I want to drain down the hot water tank which is the traditional vented design. Feed from the cold water tank at the bottom and pipe out of the top with a vented pipe going up into the loft. There is a gate valve in the feed from the cold water tank.
Turning this off certainly stops the water flow from the HW taps but I would have expected a lot more water while the HW tank drained. But it doesn't. Turn off the gate valve and immediately the hot water taps stop. The only reason that I can think of is if the vent pipe is blocked but find that very hard to comprehend how it could happen (if it has).
Confused am I.