Not all water service pipe material can be used for water distribution. For example, PVC pipe is not usable for water distribution because it cannot tolerate hot water temperatures. Therefore, water service piping materials that are not certified for water distribution should terminate at or before the full-open valve located at the entrance to the dwelling. CPVC and PEX are permitted for both water service and water distribution and, therefore, a termination and a change in pipe material would not be required.
Copper or Copper-Alloy Tubing
Copper tubing is available in Type K, L and M, which indicate wall thickness. Type K is the thickest and typically used for underground water service. Type M is the thinnest and most commonly used in water distribution systems. Type L is high-quality. Types of copper tubing are identified with color markings on the tubing: Type K is green; Type L is blue; and Type M is red. Copper pipe is soldered, but flare connections and compression fittings can also be used.
Some plumbers prefer not to use compression fittings because they sometimes leak at the connection.