This is the first document of its kind. The supplement is a separate document from the Uniform Plumbing Code and Uniform Mechanical Code and establishes requirements for green building and water efficiency applicable to plumbing and mechanical systems. The GPMCS serves as an adjunct to the Uniform Codes or any of the plumbing and mechanical codes used in the U.S. This document is designed to facilitate safe and reliable sustainable plumbing and mechanical construction practices.