I assumed Goose had a metal plug,when he talked about the anode. I have put tape on it, then again sometimes I don't. I have the anode rod in mine also. I have used Teflon tape on the nylon plugs in my pontoon boat. I didn't like how loose they felt going in. I don't need water getting in there. I found some brass plugs that will fit tight, but then you have electrolysis with the different metals. That, I don't know how big a deal it would be.
It's just easier for me to open the valve, that way I can do other things while the tank is filling. Most of the time, I'm by myself, when opening up for spring. I don't have to stand inside to make sure that air and water aren't splashing out of the sink. Plus I know for sure there is water in the tank before heating it up. I have seen people forget a bypass valve and because they were getting water out of the faucets, fired up the heater with no water in it.
Spring is upon us and I for one, is ready to go camping.