Plumbing is the system of pipes, drains, fittings, valves, and fixtures installed for the distribution of potable water for drinking, heating and washing, and waterborne waste removal. 

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 States, plumbing codes and licensing are generally controlled by state and local governments. At the national level, the Environmental Protection Agency has set guidelines about what constitutes lead-free plumbing fittings and pipes, in order to comply with the Safe Drinking Water Act.