Coconut based valve lubricant is made by Thetford or Camco. But you may have to put it in an empty tank with the coach air leveled to be low on the port side (driver's side), so when added to the tank via the toilet it will flow right to the valve, used per bottle directions. Put some down a sink trap and add water as directed to flow to the grey tank valve. Then while connected to RV park sewer, work the valves open and closed to get the lube into the gate mechanism and seals. Some spray silicone worked into the handle shafts may help also. Sometimes though, the valve seals are too far gone or gunk is stuck in the gate mechanism such that disassembly and new seals or valve is the best fix.
There's no guarantee that the Rhinoflex will work for you, but if it fits your configuration and aligns as good as mine does, it will solve the problem well. I'm not sure why the factory placed the floor port just "out of whack" with the valve outlet; guess they never had to actually hook up a hose and bayonet.
One other thing to note: when the factory installed the tanks, they used a hole saw on them to make holes for the valves. They often left the resulting plastic cut-out disk inside the tank, if it didn't come out on the end of the saw. Then poor owners (like me) wonder why, some day not long after purchase, they can't get much flow out of their valves. One weekend while parked at BCS awaiting a Monday morning service, I took the time to insert an adroitly bent coathanger up into the black tank via the valve, and wah-lah, out came the confounded black disk that had been intermittently blocking the outlet for months. I'd expected to find a washcloth or something that some kid had flushed down the toilet (Loo in England) while the coach was at an RV show before we bought it. Not. Keep this notion in mind should your system start draining slowly.
Joel
