[wingnut60]

OK, looks like you have a brand new unit? If you can't get back to the dealer (this should have been noted in the PDI if it didn't work) for warranty work, then you can try to work on it. Probably the check valve is reversed--won't allow flow in instead of outward--you will have to find where the flush line goes thru the trailer wall and take it apart. Not sure how the newer ones are set up, but I will bet this is the problem.

The check valve is there by code to keep any water that has been in the black tank from accidentally getting into the water supply lines--it isn't unusual for it to be installed backward. Just look at the line where it goes into the wall and try to find it in the plumbing area behind the basement sliding wall. May have to be a contortionist to reach it.

Good luck

Joe