About license
Years of training and/or experience are needed to become a skilled plumber; some jurisdictions also require that plumbers be licensed.
Some needed skills, interests, and values
Reading drawings, and specifications to determine layout of water supply, waste, and venting systems
Detecting faults in plumbing appliances and systems, and correctly diagnosing their causes
Installing, repairing and maintaining domestic, commercial, and industrial plumbing fixtures and systems
Locating and marking positions for pipe connections, passage holes, and fixtures in walls and floors
Measuring, cutting, bending, and threading pipes using hand and power tools or machines
Joining pipes and fittings together using soldering techniques, compression fittings, threaded fittings, and push-on fittings.
Testing pipes for leaks using air and water pressure gauges
Awareness of legal regulations and safety issues
Ensuring safety standards and build regulations are met.
United States
Each state and locality may have its own licensing and taxing schemes for plumbers. There is no federal law establishing licenses for plumbers.
United Kingdom
Plumbers in the United Kingdom are required to pass Level 2 and Level 3 vocational requirements of the City and Guilds of London Institute.
Źródło: https://en.wikipedia.org/wiki/Plumber#Plumbing_activities
Putting water and sewage network for use
Making water and sewage networks in the block by a team of plumbers, who also have their helpers. Thanks to this ongoing work can proceed quickly and efficiently. Putting water and sewage networks to use may take place after its detailed examination by different specialists. The administrator of the building depends on the fact that the network of water and sewage in the block, for which he is responsible has been operational for many years and did not have to carry it some complicated repairs. In addition, from time to time perform reviews of water and sewage networks in the block, which is required by law. Sometimes, however, there is a large block of hydraulic failure, which must be repaired by the entire human.
Interesting thing - history of word
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.5 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".6 Thus a person with expertise in working with lead was first known as a Plumbarius which was later shortened to plumber.
Źródło: https://en.wikipedia.org/wiki/Plumber