It just occurred to me that I need to flush the hot water tank as part of it's regular maintenance. I've never done it before and noticed that the drain valve doesn't have a normal handle on it. How the hell does this work? Do I just use a flathead screwdriver or a socket to turn it? Is draining it as simple as opening the valve and closing it when it's done? I've read a few sources that I need to turn off the burner and use the relief valve and then relighting the burner, but it doesn't say to do that in the manual. What's the right way?