Shower backed up
My shower drains into the grey tank without issue until the grey tank fills to halfway, then the water backs up into the shower. The kitchen sink and front bath sink will continue to drain just fine, ...
Forum Discussion
How are you determining the tank level? via the official gauges? Those are notoriously inaccurate. More so with the black than the gray, but neither are, um, really remarkably accurate/useful. And for what it is worth, the entire gray water system is designed so that when the tank gets full, it ALL backs up into the shower.
I agree with @HappyKayakers that the dump problem sounds like a cutout. When the rig makers buy the holding tanks, they have no holes in the top for input, so that they can put 'em wherever they want 'em. They drill their own with a hole saw, and often just let the cutout fall into the tank, rather than go to the trouble of fishing it out. My black tank had the cutout for the toilet in there without issue for 5-1/2 years, before it finally flushed down the drain and got stuck in the drain valve. It wasn't hard to pull on out, however.
I agree with @HappyKayakers that the dump problem sounds like a cutout. When the rig makers buy the holding tanks, they have no holes in the top for input, so that they can put 'em wherever they want 'em. They drill their own with a hole saw, and often just let the cutout fall into the tank, rather than go to the trouble of fishing it out. My black tank had the cutout for the toilet in there without issue for 5-1/2 years, before it finally flushed down the drain and got stuck in the drain valve. It wasn't hard to pull on out, however.
