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
They are usually associated with clogged drains through toilet paper and various paper thrown into the toilet bowl, as well as by a variety of dirt, which over time settle on the banks of the sewer pipe.