Sewer smell in trailer and under kitchen sink

We took one too many flushes into our black tank last week. got the same smell into the trailer as when the septic pumper comes to visit at home. From the toilet seal it looks like you have a little more room, but the vent stack must stick down into the tank a bit, so less volume than it appears.

Nasty surprise if you're not ready to dump and hit the road...only one visit to the campground facilities needed. Should have dumped the 1/2 day of travel and dry camping "deposits" when I got into the 3 night campground. Oops.

Ralph