I think what you have is enclosed, probably heated tanks and valves. It appears that your black tank valve handle has been worked on or replaced. It should be on an extension that goes thru the under belly, which should be sealed up and the valve handle is accessable from under the underbelly. I think something happened to your extension, and instead of fixing it right, they opened up the underbelly and just put a regular valve handle on it.
Your grey tank should be the same way. IOW, the grey and black pipes that are visible below the under belly when it is sealed up, never have any liquid in them (which could freeze) unless the valves are opened to dump.
