Plumbing is any system that conveys fluids for a wide range of applications. Heating and cooling, waste removal, and potable water delivery are among the most common uses for plumbing however plumbing's not limited to these applications.1 Plumbing utilizes pipes, valves, plumbing fixtures, tanks, and other apparatuses to convey fluids.2 Trades that work with plumbing such as boilermakers, plumbers, and pipefitters are referred to the plumbing trade.
In the Developed world plumbing infrastructure is critical for public health and sanitation. Źródło: https://en.wikipedia.org/wiki/Plumbing#Systems
Some plumbers also run his own business, under which perform minor plumbing services.
So they can get regular customers, who will often benefit from their services.
Much of the plumbing work in populated areas is regulated by government or quasi-government agencies due to the direct impact on the public's health, safety, and welfare..Plumbing installation and repair work on residences and other buildings generally must be done according to plumbing and building codes to protect the inhabitants of the buildings and to ensure safe, quality construction to future buyers.If permits are required for work, plumbing contractors typically secure them from the authorities on behalf of home or building owners. In the United Kingdom the professional body is the Chartered Institute of Plumbing and Heating Engineering (educational charity status) and it is true that the trade still remains virtually ungoverned; there are no systems in place to monitor or control the activities of unqualified plumbers or those home owners who choose to undertake installation and maintenance works themselves, despite the health and safety issues which arise from such works when they are undertaken incorrectly; see Health Aspects of Plumbing (HAP) published jointly by the World Health Organization (WHO) and the World Plumbing Council (WPC). WPC has subsequently appointed a representative to the World Health Organization to take forward various projects related to Health Aspects of Plumbing.Źródło: https://en.wikipedia.org/wiki/Plumbing