TRANSMISSION MAIN DESIGN
Before a water supply system is constructed or modified, the designer and contractor need to consult the local plumbing code and obtain a building permits prior to construction.
Even replacing an existing water heater may require a permit and inspection of the work. NSF 61 is the U.S. national standard for potable water piping guidelines. National and local fire codes should be integrated in the design phase of the water system too to prevent "failure comply with regulations" notices. Some areas of the United States require on-site water reserves of potable and fire water by law.
Fittings and valves
Potable water supply systems require not only pipe, but also many fittings and valves which add considerably to their functionality as well as cost. The Piping and plumbing fittings and Valves articles discuss them further.
PVC/CPVC - rigid plastic pipes similar to PVC drain pipes but with thicker walls to deal with municipal water pressure, introduced around 1970. PVC should be used for cold water only, or venting. CPVC can be used for hot and cold potable water supply. Connections are made with primers and solvent cements as required by code.