Emptying Sluggish Holding tanks
I have often found emptying the black tank on our Funfinder 189 FBS a challenge. Flushing it completely seemed a daunting task. Then, in a moment of brilliance, I discerned two things: first, the trailer is narrow (7.5') and second, the holding tanks are quite "flat" in configuration, mainly due to lack of clearance. To combat these, I simply ran my wheels on the starboard (entrance door) side up on my leveling blocks. This tilts the trailer toward the emptying valve of the black tank. Presto! Everything runs out like Niagra Falls. It takes very little rinsing to get a nice clean tank every time.