- 15105 - Pipes and Tubes
- 15110 - Valves
- 15120 - Piping Specialties
- 15130 - Pumps
- 15140 - Domestic Water Piping
- 15410 - Plumbing Fixtures
- 15510 - Heating Boilers and Accessories
- 15700 - Heating, Ventilating, Air Conditioning Equipment
- 15760 - Terminal Heating and Cooling Units
- 15770 - Floor-Heating & Snow-Melting Equipment
- 15915 - Electric and Electronic Control
- 21 05 19 - Meters and Gages for Fire-Suppression Systems
- 21 05 23 - General-Duty Valves for Water-Based Fire-Suppression Piping
- 22 05 19 - Meters and Gages for Plumbing Piping
- 22 05 23 - General-Duty Valves for Plumbing Piping
- 22 11 13 - Facility Water Distribution Piping
- 22 11 16 - Domestic Water Piping
- 22 40 00 - PLUMBING FIXTURES
- 23 05 19 - Meters and Gages for HVAC Piping
- 23 05 23 - General-Duty Valves for HVAC Piping
- 23 09 33 - Electric and Electronic Control System for HVAC
- 23 21 23 - Hydronic Pumps
- 23 50 00 - CENTRAL HEATING EQUIPMENT
- 23 52 00 - Heating Boilers
- 23 52 16 - Condensing Boilers
- 23 52 19 - Pulse Combustion Boilers
- 23 52 23 - Cast-Iron Boilers
- 23 52 33 - Water-Tube Boilers
- 23 52 39 - Fire-Tube Boilers
- 23 60 00 - CENTRAL COOLING EQUIPMENT
- 23 70 00 - CENTRAL HVAC EQUIPMENT
- 23 80 00 - DECENTRALIZED HVAC EQUIPMENT
- 23 82 00 - Convection Heating and Cooling Units
- 23 82 16 - Air Coils
- 23 82 19 - Fan Coil Units
- 23 82 23 - Unit Ventilators
- 23 82 26 - Induction Units
- 23 82 33 - Convectors
- 23 82 36 - Finned-Tube Radiation Heaters
- 23 82 39 - Unit Heaters
- 23 83 00 - Radiant Heating Units