And elbow fitting or ell is a plumbing fitting installed between two lengths of pipe or tube allowing a change of direction. The name comes form the shape of the fitting, it is shaped like an elbow with two openings that changes the direction of the line allowing water to flow in a curve.
Also referred to as an elbow, it is designed to use with pipe, tubing, conduit, or duct and is available in 90 to 45 degrees. The ends may be machined for butt welding, threaded (usually female), or socketed, etc. When the two ends differ in size, it is called a reducing or reducer elbow.
Most elbows are available in short radius or long radius elbow types. The short radius elbows have a center to end distance equal to the Nominal Pipe Size (NPS) in inches, while the long radius is 1.5 times the NPS in inches.
Short elbows are universally available; long radius elbows are readily available in acrylonitrile butadiene styrene (ABS, plastic), polyvinyl chloride (PVC) for DWV, sewage and central vacuums, chlorinated polyvinyl chloride (CPVC) and copper for 1950s to 1960s houses with copper drains.