A plumber is a tradesperson who specializes in installing and maintaining systems used for potable (drinking) water, sewage, drainage, venting, heating and air-conditioning, or industrial process plant piping.  In most jurisdictions the piping for HVAC, fire protection, and industrial systems are installed by 'steam-fitters', 'pipe-fitters', or 'gas-fitters' tradespeople. Many in these trades are members of organized labor groups, while many are nonunion. Years of training and experience are needed to become a skilled plumber; most jurisdictions also require that plumbers be licensed. A Master Plumber is one who has demonstrated mastery of the trade of plumbing, has worked in the field for many years, is certified in different areas of plumbing, typically trains new plumbers in the trade, and oversees large plumbing projects.
Unusually, in the United Kingdom the plumbing trade still remains virtually ungoverned; there are no effective 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. Furthermore, despite having in place an infrastructure dedicated to formally training plumbers and various Statutes, Regulations and Bye-laws designed to dictate and control how and in what manner plumbing works are undertaken, there is nothing to stop anyone without any training whatsoever working as a plumber, safe in the knowledge that it is unlikely that their lack of technical know-how will ever be found-out. Such people are referred to as Cowboys.
Plumbers in Reading the United Kingdom generally undertake the installation of domestic internal hot and cold water pipe work, sanitary fittings and related soil and waste pipe work systems. Domestic, commercial and Industrial gas-fired (central) heating installation, servicing and repair works, and works related to all other gas fired appliances, although undertaken by plumbers, also involves the use of other 'sub-trades' such as pipe fitters, gas fitters etc and (in the case of gas fired appliances) is ineffectively regulated by by an organisation called CORGI (with whom such individuals and organisations are supposed to be registered before working in this sphere), which although entrusted by the UK Government to control works related to this field, have no direct means of controlling or policing such works and are generally only involved in issues arising after the works are completed (and invariably, an accident has occurred). As a consequence there is a large quantity of work undertaken by unregistered, unqualified individuals, which is invariably a risk to the health and welfare of the user.
Oil fired heating appliance installation, servicing and maintenance works must be undertaken by OFTEC registered individuals and Companies in order to operate in the UK and due to the complexity of this type of installation and the relatively small number of oil burning appliances (compared to gas usage) this type of licensing is generally effective in this instance, despite OFTEC generally operating in the same way as CORGI.
Furthermore, due to the fact that air conditioning design and installation is perceived to be too complex for plumbers to undertake and legislation related to the use and correct disposal of refrigerant for use in the air-conditioning field, air conditioning is considered to be a separate trade in the UK.Plumbers install and repair pipes, fittings, fixtures, and other plumbing equipment used for water distribution, waste water disposal, and venting in residential, commercial, institutional, and industrial buildings.