- Plumbing is comprised of the pipes and fixtures (such as faucets) that make up the distribution system for water, and the removal system for waterborne waste. Facilities such as sewers and water mains are not considered to be plumbing, but instead only those systems which are part of a building are called plumbing.
- Plumbing will always consist of a network of pipes. These pipes can be made of copper, stainless steel, brass, or (increasingly common) plastic. The flow of water through these pipes is controlled by valves, that bend around corners through the use of a joint called an elbow. The end-use of plumbing comes at the fixtures, such as faucets and toilets, although some fixtures recycle water back into the building's plumbing, such as hot water heaters.
- Plumbing works because water is kept under pressure within the pipes. If a water main connection runs into the basement of a house, the water still flows on the second floor because of the pressure. In ancient times, this pressure was created by the force of gravity. In modern times, this is done with powerful pumps instead.
