I just need to check if I have understood this correctly and whether there are any risks or issues I need to be aware of.
As I understand, the water going through the hot water cylinder to the taps is supplied up the main through a tap to the cold water tank in the loft t hen down under gravity to supply the bottom of the tank through a gate valv e. If I want to drain the cylinder I shut off the tap on the side supplying the tank in the loft and shut off the gate valve supplying the hot water c ylinder. Then I attach a hose to the drain valve at the bottom of the cylin der and open the drain valve. Having shut off the gate valve the water in the cylinder wont be replaced f rom the tank in the loft. Is that it?