23.20.00 HVAC Piping and Pumps
23.25.00 HVAC Water Treatment
23.25.13 Water Treatment for Closed-Loop Hydronic Systems 23.25.16 Water Treatment for Open Hydronic Systems 23.25.19 Water Treatment for Steam System Feedwater 23.25.23 Water Treatment for Humidification Steam System Feedwater 23.25.26 Electronic Water Conditioning for HVAC Systems 23.25.33 HVAC Makeup-Water Filtration Equipment