Here's another link to help you research. It includes this picture.
http://green.blogs.nytimes.com/2012/07/16/a-mayan-water-system-with-lessons-for-today/
For more, search "Mayan water reservoir images."
I also found an article about a pressurized water system.
http://www.sciencedaily.com/releases/2010/05/100504155421.htm