Originally Posted by OldCoot
You need to keep the drain P traps filled with water. Sometimes, when you empty the grey tanks, the suction will pull the water out of the traps.
Interesting note about dumping the gray pulling the water out. I didn't know it would do that, but it does make sense.
But, I rarely dump immediately before leaving any more. I usually do it the night before. The next day I'll get a shower before we hit the road (sometimes even after I've disconnected everything).