Plumbing Supply and Remove and Replace provide online diagrams of different toilet cisterns. Contech Engineered Solutions' website, Rainfilters.com, and the Penn State Extension's Natural Resources Program are resources for diagrams of typical underground rainwater-harvesting cisterns.
Diagrams of toilet cisterns vary depending on desired plumbing technology. The San Francisco Chronicle suggested in 2011 that the best way to find information on different types of cisterns is to visit the websites of various manufacturers. The Chronicle further stated that the newer cylindrical model is more effective and efficient than the rod-and-ball floater model common in older toilets. Common toilet cistern diagrams featured by home repair sites such as Remove and Replace clearly identify the main cistern valves and their component parts. Main features of a toilet cistern are the fill valve, which fills the tank with water, and the flush valve, which empties the cistern's water into the toilet bowl during flushing.
Penn State Extention's Natural Resources Program provides online diagrams and descriptions for several types of underground rainwater cisterns as well as step-by-step instructions on cistern construction and maintenance. Penn State Extension also provides cut-out diagrams of smaller individual pieces of the cistern system and several tables to suggest optimum cistern size.