The tank is still vented the little tank on top is the fill and expansion so it's still a standard tank the fortic tanks were made for when you didn't have enough room for the separate tank, to drain down you would still need to release pressure so you could open the hot taps and try the drain c o c k, just make sure you tie the ball valve up in the little tank at the top that will stop it re filling if you can't turn the water off.