Wall thickness does not affect pipe or tubing size. 1/2" L copper has the same outer diameter as 1/2" K or M copper. The same applies to pipe schedules. As a result, a slight increase in pressure losses is realized due to a decrease in flowpath as wall thickness is increased. In other words, 1 foot of 1/2" L copper has slightly less volume than 1 foot of 1/2 M copper.
Plastic pipe is in wide use for domestic water supply and drain-waste-vent (DWV) pipe. Principal types include: Polyvinyl chloride (PVC) was produced experimentally in the 19th century but did not become practical to manufacture until 1926, when Waldo Semon of BF Goodrich Co. developed a method to plasticize PVC, making it easier to process. PVC pipe began to be manufactured in the 1940s and was in wide use for Drain-Waste-Vent piping during the reconstruction of Germany and Japan following WWII. In the 1950s, plastics manufacturers in Western Europe and Japan began producing acrylonitrile butadiene styrene (ABS) pipe. The method for producing cross-linked polyethylene (PEX) was also developed in the 1950s. Plastic supply pipes have become increasingly common, with a variety of materials and fittings employed.
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.