Grey tank for shower won’t empty? Dump valve opens and closes yet won’t drain.

[mlhrad]

See above

[happycamperz]

Silly question, are you sure there is stuff in the tank? Those in tank sensors are known to have funk stuck to them and show the tank is more full than it really is.

[TripleEEE]

Is it a cable actuated valve?

It handle/cable may have become detached from the valve itself and not actually opening the valve.

Please state, year, make, model of coach. We can help you better with more information.

[nothermark]

Open the gray tank valve and dump 5 gallons of water in the shower and see what happens.

[Mudfrog]

I'm not sure if any of the valves are made like this or not but,, could it be that the T handle has simply unscrewed from the slide valve?

If you're sure there's liquid in the tank, then it may be a stoppage where the drain pipe leaves the tank or at the valve.

[hohenwald48]

New motorhome or old motorhome. New to you? Has it ever dumped properly? You gotta' give us some clues here.

[CJ7ole]

There shouldn't be anything going down the drain into your grey tank that would cause a stoppage. Unless something crawled up the hose into the tank.
That is a scary thought isn't it? So it is either a bad valve/actuator or your tank is empty.