Building a water barometer is remarkably easy and dramatic way for students to learn about. the amazing properties of air pressure. Staring up at a column of water 33-ft height that is supported only by the weight of the atmosphere has a way of impressing upon students the power and importance of air pressure. Not only can students develop an intuitive understanding of pressure and how barometer works they also extend the experiment to explore vapor pressure phase changes equilibrium and gas solubility. Best of all this experiment is inexpensive to set up and can be completed within a single 45-min class period.