Uniform Mechanical Code

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Full nameInternational Association of Plumbing and Mechanical Officials
Key peopleGP Russ Chaney, CEO; Bruce Pfeiffer, President; DJ Nunez, Vice President; Hugo Aguilar, Vice President of Codes and Standards; Zalmie Hussein, Code Development Administrator
CountryUnited States

Designated as an American National Standard, the Uniform Mechanical Code (UMC) is a model code developed by the International Association of Plumbing and Mechanical Officials (IAPMO) to govern the installation, inspection and maintenance of HVAC (heating, ventilating and air-conditioning) and refrigeration systems.

The UMC is developed using the American National Standards Institute's (ANSI) consensus development procedures. This process brings together volunteers representing a variety of viewpoints and interests to achieve consensus on mechanical issues.

The UMC is designed to provide consumers with safe mechanical systems while, at the same time, allowing latitude for innovation and new technologies. The public at large is encouraged to provide input for the development process. The code is updated every three years. A code development timeline and other relevant information are available at IAPMO’s Website.


In 1926, a group of Los Angeles plumbing inspectors recognized that there were no uniform requirements for the installation and maintenance of plumbing systems. At that time, heating was done by boilers that piped the heat to radiators. Efficient air conditioning was not available. Widely divergent practices and the use of many different, often conflicting, plumbing codes by local jurisdictions led to plumbing systems that were incompatible and potentially dangerous.[1] This underscored the necessity of developing a model code that could be uniformly applied across jurisdictions.

Two years later, the city adopted the first version of a uniform plumbing and mechanical code developed by the Los Angeles City Plumbing Inspectors Association (LACPIA) and based on the input from a committee of plumbing inspectors, master and journeyman plumbers, and mechanical engineers, assisted by public utility companies and the plumbing industry.

The ultimate product of this effort, the first Uniform Mechanical Code, was published by IAPMO, the new name for LACPIA, which was adopted in 1966 when the scope of mechanical work grew beyond plumbing and became more readily available in residential applications.[1] in 1967. Over the last fifty years, this voluntary code has been adapted by jurisdictions not only throughout the United States, but internationally as well. The consensus development process was first applied to the 2003 edition.

The 2012 edition is the fourth edition developed under the ANSI consensus process. Contributions to the content of the code were made by every segment of the building industry, including such diverse interests as consumers, enforcing authorities, installers/maintainers, insurance, labor, manufacturers, research/standards/testing laboratories, special experts, and users. The 2012 Uniform Mechanical Code is supported by the American Society of Sanitary Engineering (ASSE), the Mechanical Contractors Association of America (MCAA), the Plumbing-Heating-Cooling Contractors National Association (PHCC-NA), the United Association (UA) and the World Plumbing Council (WPC).

2018 Edition[edit]

Major changes include:


  • Chapter 1 - Administration
  • Chapter 2 - Definitions
  • Chapter 3 - General Regulations
  • Chapter 4 - Ventilation Air
  • Chapter 5 - Exhaust Systems (Part 1: Environmental Air Ducts and Product Conveying Systems; Part 2: Commercial Hoods and Kitchen Ventilation)
  • Chapter 6 - Duct Systems
  • Chapter 7 - Combustion Air
  • Chapter 8 - Chimney and Vents
  • Chapter 9 - Installation of Specific Appliances
  • Chapter 10 - Boilers and Pressure Vessels
  • Chapter 11 - Refrigeration (Part 1: Refrigeration Systems; Part 2: Cooling Towers)
  • Chapter 12 - Hydronics (Part 1: Steam and Water Piping; Part 2: Hydronic Panel Heating Systems)
  • Chapter 13 - Fuel Gas Piping (Part 1: Fuel Piping; Part 2: Fuel Supply: Manufactured/Mobile Home Parks and Recreational Vehicle Parks)
  • Chapter 14 - Process Piping
  • Chapter 15 - Solar Energy Systems
  • Chapter 16 - Stationary Power Plants
  • Chapter 17 - Referenced Standards
  • Appendix A - Residential Plans Examiner Review Form for HVAC System Design
  • Appendix B - Procedures to be Followed to Place Gas Equipment in Operation
  • Appendix C - Installation and Testing of Oil (Liquid) Fuel-Fired Equipment
  • Appendix D - Fuel Supply: Manufactured/Mobile Home Parks and Recreational Vehicle Parks
  • Appendix E - Sustainable Practices
  • Appendix F - Sizing of Venting Systems and Outdoor Combustion and Ventilation Opening Design
  • Appendix G - Example Calculation of Outdoor Air Rate

See also[edit]


  1. ^ a b "1926 to 2006: Eight Decades of Excellence," Copyright © 2007 by IAPMO, p. 47-9

External links[edit]