Black Tank Plumbing in a 3791RD

[Cindy and Ray's Grand Tour]

Does anyone know if a 3791RD has regular or angled pipe going into the black tank? I am plugged up down there somewhere and would like to get a "twister plunger" but it will not work with angled piping to the black tank. It has to be straight down. The plug is in the down pipe or at the bottom. The tank backfills and drains just fine. I used an auger to create enough room for water to drain down but it still burps and you can hear the water slowly draining below the floor. Thus no solids can be used yet.