ya gotta have water in the bowl first.... if you try to use it with a dry bowl, it could be messier than it was designed to be.I bought the Thetford Porta Potti Curve this year. I like the higher height. I'm not sure about a bowel movement though... seems like a messy endeavor for any porta potti getting the 'goods' to go down into the tank.
http://www.amazon.com/Thetford-9236...=1340677246&sr=8-1&keywords=porta+potti+curve