O'Brien Mechanical, Inc. II is a family-owned, full-service Plumbing/Piping/HVAC contractor that self-performs a wide range of plumbing and piping installation work for commercial projects throughout the Greater Bay Area. Headquartered in San Francisco, OBMI's professional staff and trades people deliver full design, construction, and fabrication for complex plumbing, piping, and HVAC systems. First established in 1970 as O'Brien Mechanical and later changed to O'Brien Mechanical, Inc. II in 1998, today, OBMI employs over 90 union-affiliated and administrative employees generating well over $18 million in annual revenue. Our company advocates innovative engineering, advanced technology, quality craftsmanship, maximum efficiency, minimum waste, on-time scheduling and excellent customer service from beginning to end. Some of the Bay Area's most reputable building owners, managers, architects, engineers, and general contractors have been entrusting their plumbing/piping/HVAC systems to OBMI for over half a century.



  • Radisson Hotel Renovation (250 Rooms), San Francisco
  • Holiday Inn (240 Rooms), San Francisco
  • Tuscan Inn (250 Rooms), San Francisco
  • Harbor Court Hotel (140 Rooms), San Francisco
  • Harry Denton's Restaurant, San Francisco
  • Embarcadero YMCA, San Francisco


  • New Moscone Center Convention Center, San Francisco
  • United Airlines at the San Francisco International Airport
  • Hearst Corporation Newspaper Agencies Plants, San Francisco, Union City, & Richmond
  • St. Cecilia's Church & Teen Center, San Francisco
  • State of California - Transbay Terminal, San Francisco
  • Budweiser Industrial Warehouse, San Francisco


  • UCSF Stanford Health Care - Mount Zion Cancer Center, San Francisco
  • Jewish Home for the Aged, San Francisco
  • Larkin Street Health Clinic, San Francisco
  • U.S. Veterans Ambulatory Facility, San Francisco


  • Charles Schwab Building - 101 Montgomery Street, San Francisco
  • Wells Fargo Headquarters, California Street, San Francisco