Facts from Wikipedia
Water systems of ancient times relied on gravity for the supply of water, using pipes or channels usually made of clay, lead, bamboo, wood, or stone. Hollowed wooden logs wrapped in steel banding were used for plumbing pipes, particularly water mains. Logs were used for water distribution in England close to 500 years ago. US cities began using hollowed logs in the late 1700s through the 1800s.8 Today, most plumbing supply pipe is made out of steel, copper, and plastic; most waste (also known as "soil")11 out of steel, copper, plastic, and cast iron.11
The straight sections of plumbing systems are called "pipes" or "tubes". A pipe is typically formed via casting or welding, whereas a tube is made through extrusion. Pipe normally has thicker walls and may be threaded or welded, while tubing is thinner-walled and requires special joining techniques such as brazing, compression fitting, crimping, or for plastics, solvent welding. These joining techniques are discussed in more detail in the piping and plumbing fittings article.
Plumbers and their "toys" - reason we call them
When it comes to professional repairs done by specialists, you often wonder - "ha, I could do that myself, but now I need to pay anyway...". It is common enough way of thinking, but is it really true?
Experts in their fields make it look like it is easy, but only because they have years of experience. Because of it, they were able to deduce what the problem is quickly, and if it is easy to fix, they make it look like it's nothing. It may escape your attention, but they more often than not, use special tools when doing so.
Simple wrench and hammer are common household items, but what about thread seal tape? Or do you really want to buy whole package od putty, just to seal one small hole? These are the things that seperate experts in their fields from weekend handyman. Other than that, they are also the reasons why you call in a real plumber, once in a while.
Plumbers and their heritage by Wikipedia
Wikipedia provides us with brief history of the plumbers:
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.