Plumbers install and repair water, waste disposal, drainage and gas systems, plumbing fixtures and appliances. Most states and communities require plumbers to be licensed, according to the Bureau of Labor Statistics (BLS). However, licensing requirements vary. The BLS indicates that a typical licensing requirement for a plumber to work independently is two to five years of experience and passing an examination that tests knowledge of plumbing and of local plumbing codes
Why License Plumbers?
States and communities license plumbers to ensure that they follow clear standards to protect the health and safety of people living in the community. Contaminated drinking water or accidents caused by plumbing failures can be a serious problem.
According to the article "Plumber licensing: Experts explain reason for hefty regulations" on the website Angie's List, plumbers are licensed at the state level in 44 states. Licenses are not usually transferable from state to state. In some states, many cities or counties also require city or county licensing. The disadvantage to individual city or county licensing is that plumbers have to have a license from every city or county where they do plumbing jobs.
Both the education requirements and testing requirements for obtaining a plumbing license vary from location to location. Some places have practical tests and others have only written exams. If you want to become a plumber, it's important to know the requirements of the location where you want to work.
Some states also require specialty licenses for plumbers who want to do specific types of jobs, such as backflow prevention testing and repair, underground work, water softening and filtration or electric control wiring.