Originally Posted by kz08h5
The black tank valve can be opened but nothing comes out so it is frozen.
Uh oh....the dreaded POOPSICLE!!
Looks like you're already working on figuring out your tank heaters. Even if you find out that the heaters you have are working, and you still freeze up at the valves, I known people who have had to make a temporary enclosure around the valve and use electric (or propane) heaters to thaw out their poopsicle to be able to dump. A small roll of reflectix works to enclose the valve, then throw as much heat at it as you can.