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. Plumbing
also refers to the skilled trade which deals with installation and maintenance.
The plumbing industry is a basic and substantial part of every developed economy. Plumbing
often denotes the supply and waste system of an individual building distinguishing it from water supply and sewage systems that serve a group of buildings.
A fitting is used in pipe plumbing systems to connect straight pipe or tubing sections to adapt to different sizes or shapes and for other purposes such as regulating or measuring fluid flow. The term plumbing is generally used to describe conveyance of water gas or liquid waste in ordinary domestic or commercial environments whereas piping is often used to describe high-performance conveyance of fluids in specialized applications.
The term tubing is sometimes used for lighter-weight piping especially types that are flexible enough to be supplied in coiled form. Fittings require money time materials and tools to install so they are a non-trivial part of piping and plumbing systems. Valves are technically fittings but are usually discussed separately.