The two major categories of plumping pipe are plastic and metal. Plastic pipes include polyvinyl chloride (PVC), chlorinated polyvinyl chlorine (CPVC), PEX pipe and PolyPipe®. Copper, stainless steel and galvanized steel are all types of metal plumbing pipe. Not all pipes are as useful or effective as others, and each type is used for a specific purpose in plumbing.
PVC pipe is a type of plastic plumbing pipe primarily used to transport high pressured water. It is available in several standard sizes, ranging from ½ inch (1.3 centimeters) to 4 inches (10.2 centimeters) in diameter. PVC pipe is only made to handle cold water, as hot water will cause the pipe to warp. It is generally white in color, though a few varieties are gray.
CPVC is PVC pipe that has received an extra chlorination. It comes in a distinctive yellow color, and can handle both hot and cold water. CPVC is more flexible with substantially thinner walls than PVC pipe, and has the same outer diameter as copper pipe, which increases it's range of uses.
PEX pipe, also known as cross linked polyethylene pipe, was first manufactured in the 1920s, but has become more popular in recent years. It shares the same outer diameter as copper, and can be used for both hot and cold water. However, PEX pipe has a much higher heat resistance than most other plumbing pipe, and is often used in water-based heating systems. It comes in a creamy white color, as well as red and blue which is used to denote hot and cold pipes respectively.
The final type of plastic plumbing pipe is PolyPipe®, a thick black pipe used to transport highly pressurized water, usually to and from the home. It is used almost exclusively outdoors, and is usually buried underground to prevent freezing. PolyPipe® is extremely rigid, and is rarely used for other purposes.
Copper is the most common type of plumbing pipe used in the home, although it is more expensive than plastic piping. Copper is especially resistant to corrosion, and can withstand high temperatures. Copper pipes come in three different sizes – type M, L, and K. Type M has very thin walls, while type L is of medium thickness, and type K is the thickest of the three.
Stainless steel pipe is less commonly used than other metal pipes, as it is more expensive and harder to find. It is primarily used in marine environments because it can withstand salt water, which would erode most other metal pipes. The price makes it less desirable for other applications, or in safer areas where a copper pipe would perform just as well.
Galvanized pipes have been used in homes for years, typically to carry water in and out of the house. The galvanized coating prevents rusting, and gives a dull gray appearance. Use of these heavy duty pipes is diminishing, as it is being replaced by PEX pipe, which is less expensive and just as durable. Galvanized pipes typically come in sizes between ½ inch (1.3 centimeters) and 2 inches (5.1 centimeters) in diameter.