Plumbers, pipefitters, and steamfitters may use many different materials and construction techniques, depending on the type of project. Residential water systems, for example, use copper, steel, and plastic pipe that one or two plumbers can install. Power plant water systems, by contrast, are made of large steel pipes that usually take a crew of pipefitters to install. Some workers install stainless steel pipes on dairy farms and in factories, mainly to prevent contamination.
Journeyman plumber: Once the requirements of an apprenticeship are fulfilled, plumbers can apply for a journeyman license. Many workers in the plumbing industry are journeymen. Obtaining a journeyman's license requires a fee and the successful passing of an exam. Licenses vary by state, although not all areas require journeymen to be licensed. Instead, the amount of work they are able to perform is limited.