[Pathfinder75]

Originally Posted by Rangoon

Mrs. "Rangoon" here.
On my second gray tank in the back of the RV, the valve appears to be stuck tight - possibly rusted? I discovered this because the water is backing up into my kitchen sink and I'm unable to get the gray tank open to drain. I am parked in my backyard and not able to move the RV for several months. ................
Does anyone have any suggestions .............. At least for getting the water out? Possibly siphon it???...............
(. So far I've had some very good advice from you people and REALLY appreciate this forum)!

Regarding need to drain now question
OPTION 1. With some peeking into underbelly your helper should be able to find location of valve on the tank. Cut access hole in corraplastic to it. Can tape or use tin to replace material on coroplastic when done.
Can disconnect handle.cable or rod that operates valve. If the cable/rod is problem then open. Valve by hand.
IF VALVE FROZE then a messy valve unbolt and grey water spill.to ground will be required.
OPTION 2. Under sink remove trap pipes so straight access into floor and tank. Insert hose down into tank and using cheap drill pump or MAYBE siphone water out side by running hose out the door lower than the tank.

Then fix problem with needed repair.
Good luck.