The kinetic energy of the mass of exhaust gas carries it along the exhaust pipe, and causes a pressure build up ahead of the mass of gas and a partial vacuum behind it. This principle is used in a tuned exhaust system.
Culligan - $2352 ($2053 w/o R/O unit) Culligan Gold Series (10), Good Water Machine. If I were to look at price only, I would go with either the cheaper Ecowater system w/R/O at $2698 or the Culligan system. At almost $4k, the Kinetico system seems greatly over priced.
Convenient and easy to use, the Culligan RV-EZ-3 produces cleaner, better tasting drinking and cooking water while you are on the move. The RV-EZ-3 water filter is a Level 3 Advanced Filtration system designed to be used in RV's or marine applications.