We had a nice, brand new porta-potty in our truck as we left Michigan for a run to California. It worked very well... just go into the bowl and when done, quickly open the trap door and flush water at the same time so no odor escaped from the tank. We tested it on a camping trip and it was the perfect answer to the problem of late night relief runs!
Well, we headed west across America and stopped along the way to eat here and there until night fell and I settled into a long night shift of mountain driving. We had not used the porta-potty yet but somewhere around 15,000 feet I heard my sleepy wife get out of bed and stumble over to relieve herself, then I heard her lift the cover, sit down, and heard her welcome the relief. Then she stood up and turned around to do the "quick open trap door and flush trick" which made a strange WHOOSH noise, followed by a whole bunch of sailor quality swearing and screaming!!!!
Apparently, the holding tank was not vented at all and, between 600' above sea level in Michigan and the 15,000' elevation we were currently at, a tremendous amount of pressure waited for her to quickly open the trap door of the holding tank, which blew the former contents of her bladder all over her sleepy face and shirt, causing the profanity filled outburst!!!
Well the bright side I guess was she obviously now wide awake and ready to drive for quite awhile before the possibility of falling back asleep!
The bad side was that every time I was close to falling asleep the rest of the night I heard another sharp cuss word which, honestly, evoked a VERY guarded giggle from me.
To this day we laugh heartily when we think back to the night we discovered the hard way that good porta-pottys are not vented!!!
