On 12/13/2019 at 6:52 PM, Ronbo said:

I abandoned the valves buried in the belly installed by the manufacturer. They are left open. I added new valves to the pipes on the exterior of the rv. Easy to repair and use. For your leaky valves, try adding 1 cup of cooking oil to each tank after you empty them. It will lubricator the blades and seals. 

Repeat at least 5 times:  Xlnt plan!!

*If*  you're worried about freezing temps - wrap with some elect heat tape, or some other plan B.

~

Before you start working on those valves, raise the right side and dump. Then before you remove the valves, raise the left side and any drips that are left in the tank will be away from the valve. No Mess.........

Richard