The 2004 Supplement to the 2003 National Standard Plumbing Code offers updated codes for the plumbing industry. This supplement has been endorsed by the American Society of Plumbing Engineers as well as the National Standard Plumbing Code. This is an essential read for engineers, contractors and inspectors who are members of the National Standard Plumbing Code Committee. This document contains the formal and editorial changes that were accepted by the code committee during August 21, 2003 public hearing. This document should be used in conjunction with the 2003 code.