Here are some helpful links to websites that might interest you.
American Ground Water Trust
National Ground Water Association
Air Conditioning & Refrigeration Institute
Compressed Gas Association, Inc.
Gas Appliance Manufacturers Association
International Association of Plumbing and Mechanical Officials
ASHRAE - The American Society of Heating, Refrigerating and Air Conditioning Engineers, Inc.
Plumbing-Heating-Cooling Contractors National Association
Radiant Panel Association
Water Quality Association
Water Systems Council