Low point drains and functionality

The plumbing and physics (that gravity thing) team up to make that happen. Cold water enters the bottom of the HW tank and hot water leaves from the top. When you open the cold drain it does drain the HW tank if you have some HW faucet open. You only have to do this when winterizing, not after each trip. When you want to drain the system open all faucets and both low point drains. 

I hadn't even thought about opening the faucets at the same time.  Makes sense.

Regarding having a low-point drain constantly dripping I suspect you would need to: A) turn off any water coming INTO the camper and then, B) Remove the white water cap ON THE WHITE drain hose (being careful not to be underneath when the water comes gushing out) and then use plumbers tape to wrap around the fitting before finally, C) replacing the cap, screwing it back on as tight as you dare, being VERY careful, as has been previously mentioned by others, not to twist the hose itself. It is possible of course that the cap itself may be cracked. Stuff happens. Adding an inline water pressure reducer to the water intake hose at the campground spigot will protect your hoses from bursting and may slow or even stop the drip as well. Experience is a great teacher, sad to say. Speaking of experience, just remember to take the reducer with you when you leave . . .