Elements of a Plumbing System
It is often said that the primary purposes of a plumbing system are
• To bring an adequate and potable supply of hot and cold water to the inhabitants of a house, and
• To drain all waste water and sewage discharge from fixtures into the public sewer or a private disposal system.
The piping of a house underground piping should be as short as possible. Elbows and bends should be kept to a minimum because they reduce water pressure and, therefore, the supply of water to fixtures in the house. The house service line also should be protected from freezing. Four feet of soil is a commonly accepted depth to bury the line to prevent freezing. This depth varies, however, according to the average external temperature.
The minimum service line size should be 0.75 inch. The minimum water supply pressure should be forty pounds per square inch, no cement or concrete joints should be allowed, no glue joints between different types of plastic should be allowed, and no female threaded PVC fittings should be used.
The supply mains should have a drain valve stop and waste valve to remove water from the system for repairs. These valves should be on the low end of the line or on the end of each fixture riser. Care must be taken when choosing the piping materials.