Although plumbers, pipefitters, and steamfitters perform three distinct and specialized roles, their duties are often similar. For example, they all install pipes and fittings that carry water, steam, air, or other liquids or gases. They determine the necessary materials for a job, connect pipes, and perform pressure tests to ensure that a pipe system is airtight and watertight. Their tools include drills, saws, welding torches, and wrenches.
The word "plumber" dates from the Roman Empire. The Latin for lead is plumbum. Roman roofs used lead in conduits and drain pipes and some were also covered with lead, lead was also used for piping and for making baths. In medieval times anyone who worked with lead was referred to as a plumber as can be seen from an extract of workmen fixing a roof in Westminster Palace and were referred to as plumbers "To Gilbert de Westminster, plumber, working about the roof of the pantry of the little hall, covering it with lead, and about various defects in the roof of the little hall". Thus a person with expertise in working with lead was first known as a Plumbarius which was later shortened to plumber.