ASHRAE 191P is a proposed standard setting minimum performance requirements for mechanical and process systems as well as a required water balance analysis for all water sources and sinks within a building and site. The presentation briefly discusses the history of the standard, define scope of how this standard interacts with other standards such as plumbing and irrigation standards, and highlight key requirements of each section covering everything from cooling towers to vivarium animal watering systems. Finally, examples of whole building water balances are shared to demonstrate how to apply the standard for different building types.