There are 3 types of plumbers; Commercial plumbers, Residential plumbers, Service and Repair. There are also some types of plumbers which are not, strictly speaking, plumbers at all, but rather heating engineers or bathroom fitters. There is lots of cross over between what people mean when they refer to plumbers, since many who undertake wet plumbing work will also undertake work involving gas such as boilers and fires. These types of plumbers are actually heating engineers really but the majority will likely be referred to as plumbers, and they may even refer to themselves as plumbers rather than heating engineers. Another name for the plumbers who carry out gas work is 'gas-safe plumbers'. These types of plumbers are registered on the 'gas safe register' and carry a card to identify their status as gas-safe registered. Those who carry out bathroom fitting could be considered bathroom fitters but they probably can also fix leaking taps, sinks and toilets so could be considered wet-plumbers too. The obvious split mentioned very early on in the answer is the one regarding who the plumber deals with. Commercial plumbers tend to operate in the B2B arena and deal with businesses rather than householders. The domestic plumbers deal with B2C customers (domestic householders) and the service and repair sector plumbers likely deal with both but only dealing with small jobs and general ongoing maintenance either on contracts with companies or on call outs and the like with homeowners.