Well, it's a 3" gate valve fitted to the bottom of the tank?
It is fitted to the bottom of the tank, but toward one end or the other, not the bottom center where it sags. If you ever need to go into the belly you'll see what I'm talking about. I realized all this when I did some modifications to the overflow and added a shut off valve so I could top off the tank. I found a leak in outlet connection to the pump. When I pulled the connection out I happen to look inside the tank with my scope for whatever reason. That's what started me down the path...I would have been better off not looking.