Pipe fittings cover many components that connect pipe ends for in-line, offset, multi-port, and mounting configurations. Pipe and pipe fittings are manufactured from a wide variety of materials for the transport of an equally wide variety of solids and fluids. Fitting cross sections are often, but not necessarily, circular in shape to mate with the pipe sections they are connecting; systems are typically configured with straight sections connected by fittings or specially-formed connections and joints. They are used in pressurized applications and non-pressure applications such as drain, waste, and vent (DWV) systems. Pipe fitting construction and material specifications are application-dependent; user consultation with fitting suppliers is typical for optimization of component selection.

Common types of pipe fittings include adapters, pitless adapters, bulkhead fittings, caps, compression fittings, rigid couplings, flexible couplings, cross or 4-way fittings, 90 degree elbows, 45 degree elbows, reducing elbows, end bells, expansion joints or couplings, ferrules, flanges, nipples, offset fittings, plugs, concentric reducers, eccentric reducers, returns or traps, side outlet elbows, side outlet tees, standard tees, reducing tees, bullhead tees, unions, standard wyes, and reducing wyes.  Some pipe fittings have a swivel feature that allows one or more fitting ends to rotate or swivel.

Size is the most important parameter to consider when specifying pipe fittings.  Choices for sizes include Standard English sizes, metric sizes, and schedule.  Standard English sizes range from 1/8” to greater than 36 “.  Common metric sizes range from less than 10 mm to greater than 1000 mm.  The American National Standards Institute (ANSI) assigns "schedule numbers" to classify wall thicknesses for different pressure uses. ANSI schedule numbers cover all pipe and fitting sizes from NPS 1/8 through NPS 36 identified as Standard (STD), Extra Strong (XS) and Double Extra Strong (XXS) and all wall thicknesses by ANSI schedule number.   This selection is only for fittings that mate with pipe conforming to an ANSI schedule number.  Many types of fittings do not carry this designation.  Section shape choices include round, oval, square, and rectangular.  

Common materials of construction for pipe fittings include ABS, aluminum, brass, bronze, carbon or graphite, ceramic or ceramic lined, clay or vitrified clay, concrete, CPVC, EPDM, fiberglass or composite, fluororesin (PFA), glass or glass lined, gray or cast iron, ductile iron, lead, neoprene, rubber or elastomer, nylon or polyamide, polyethylene (PE), polypropylene (PP), PTFE or PTFE lined, polyvinyl chloride (PVC), carbon and alloy steel, stainless steel, titanium, and zirconium.  Fitting end choices for pipe fittings include male pipe thread, female pipe thread, male straight thread, female straight thread, plain end, bell or socket, or flare, flange, compression fitting, pipe clamp end, barb or rib, and groove.  Common features include, lined, plated, insulated, and underground rated.

Engineering Calculators Related to Pipe Fittings Loss in Fluid Lines Calculator; Open Channel Flow Calculator; Pressure Loss in Straight Liquid Lines Calculator