Water Heaters-Parts & Supplies (Wholesale) is a subdivision of the Plumbing and Heating Equipment and Supplies (Hydronics) (Wholesale) industry. This industry involves the wholesale distribution of parts and supplies for water heaters. These parts and supplies include but are not limited to: thermostats, heating elements, gas valves, pilot assemblies, thermocouples, anode rods, pressure relief valves, and temperature and pressure relief valves. Companies in this industry typically sell their products to plumbing and heating contractors, as well as to retailers who specialize in plumbing and heating supplies.