vented system

Hello All, Just wanted to get some feedback on a system design I came up with. I understand that in a vented system the water in the tank should remain below 20 degrees to prevent legionella but it never made sense why you would route the hot water vent pipe back into the tank. I took...

My air separator (Tower AIR22CF with cold feed) is blocked with magnetite, not an issue. A straightforward simple replacement along with some associated pipework to keep things new, shiny and clean, so I thought. I was looking at the specs Tower provide and note they state a minimum distance of...