Originally Posted by Raider712
Water isnít even getting to the tank. Both of my grey tank valves are open since Iím connected to a sewer line. Iíve tried disconnecting the galley hose,, leaving the valvue open and running kitchen sink. No water comes out of the open valvue just sink fills up.
First, since this is a 2019 trailer. Would you tell us whether it ever drained, or has this always been "slow/stopped up" ???
If it drained, but now doesn't, then:
Are you POSITIVE the slide valve body is open??? Or are you relying on seeing the handle/rod assembly in the open position???? Frequently the rod will separate from the slide valve body and even though you "feel resistance" and "see the rod slide in the frame" the actual rod/valve body connection is loose and the valve body is not moving. If you can, reach your hand into the sewer opening and feel whether the slide valve body is clearing the drain opening. My guess would be that the valve slide body is not opening to allow the tank to drain.
If it has NEVER drained properly, then there is something between the sink P trap and the top of the gray tank that is causing the problem. It could be construction debris either in the drain pipes or a stoppage where the drain plumbing connects to the top of the gray tank. If you removed the air inlet trap at the top of the drain vent stack under the sink and it didn't flow, then either the tank is full or the line is plugged.
Again, I'd first verify the valve slide body is functional, then start working from the sink to the gray tank inlet. Much of your plumbing is above the floor and should be relatively easy to get to.