Originally Posted by sailingdog
This is true, but can be accomplished by flushing the tank and pumping it out again usually.
As marine sanitation professional, when I'm at the pumpout station, emptying my pumpout boat, I DO NOT
want to open a valve and have someone's leftovers out spill out. And realistically, most boatowners are not going to go to the trouble of rinsing their tanks. And even if they do, I still want 'em to do a clean-water flush of the pumpout hose before hanging it up.