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Pipe and Fittings Glossary

Tackling any plumbing project requires knowledge of different types of pipes and fittings. Here's a list of common terms and products used to complete basic plumbing projects.

Pipes and Fittings

Glossary of Terms

A - C

ABS (acrylonitrile butadiene styrene): a group of plastics made from polymers with prescribed percentages of acrylonitrile, butadiene and styrene

adapter: a fitting that joins two different pipes together or one that joins threaded with non-threaded pipe

aging: the effect on materials exposed to an environment for a period of time or the act of exposing materials to an environment for a period of time

beam loading: the process of applying a specified force (load) to a piece of pipe that's supported at two points. it's usually expressed in pounds per distance between the centers of the supports.

belled-end: a pipe end that has been enlarged to have the same inside dimensions as a fitting socket. it acts as a coupling when joining pipe.

bend (elbow): changes the direction of a pipeline a certain number of degrees

bushing: connects two pipes of different diameters

cap: a plug inserted into the end of a pipe to close it off

cleanout: a fitting with a removable element that allows access to drains without requiring the removal of plumbing fixtures

condensation: a chemical reaction involving the combination of molecules resulting in the elimination of a simple molecule, such as water, and the formation of a more complex compound of greater molecular weight

coupling: a fitting that joins two pieces of pipe or other fittings together

crazing: small, fine cracks on or under the surface of a plastic

cross: connects four pipe sections together

cure: to change the properties of a polymer to a stable, usable and final state by the use of chemical agents, heat or radiation

D - F

deflection temperature (heat distortion): the temperature that causes a plastic specimen to deflect a certain distance when a specified load is applied

degradation: the process where the chemical structure, physical properties or appearance of plastics deteriorates

dimensional stability: the capability of a plastic part to maintain its original shape and dimensions under conditions of use

dynamic pressure: the pressure when water is flowing

elasticity: the property of a plastic that allows it to return to its original dimensions after deformation

elongation: the percentage of the original length that a material will deform, under tension, without failing

environmental stress cracking: cracks that develop when a plastic part is subjected to incompatible chemicals and put under stress

extrusion: the process used to continuously form a shape by forcing a heated or unheated plastic through a shaping orifice (die)

filler: a relatively inert material added to a plastic to modify its strength, permanence, working properties or other qualities

flexural strength: the measure of a material’s ability to withstand a specified deformation under a beam load (bending) at 73°. It's normally expressed in pounds per square inch.

flush bushing: a fitting that joins two pipes of different diameters (the larger pipe screws onto the male end and the smaller pipe onto the female end)

forming: a process in which the shapes of plastic pieces, such as sheets, rods or tubes, are changed to a desired configuration

fuse: to join plastic parts by softening the material with heat or solvents


G - N

hoop stress: the circumferential stress imposed on a pipe wall when exposed to an internal pressure load. it's usually expressed in pounds per square inch.

impact strength: a measure of a plastic part’s ability to withstand the effects of dropping or striking

injection molding: the process used to form a shape by forcing a heated plastic, in a fluid state and under pressure, into the cavity of a closed mold

joint: the point where a pipe and fitting or two pieces of pipe are connected together

lubricant: any substance that reduces the friction between moving solid surfaces

modulus: the load required to cause a specified percentage of elongation. it's usually expressed in pounds per square inch or kilograms per square centimeter.

nonflammable: incapable of supporting combustion


O - R

plastic: a material that contains, as an essential ingredient, one or more organic polymeric substances of large molecular weight, is solid in its finished state and, at some stage in its manufacture or in its processing into finished articles, can be shaped by flow

plastic pipe: a hollow cylinder of a plastic material in which the wall thicknesses are usually small when compared to the diameter and in which the inside and outside walls are essentially concentric

plug: used to plug or seal an unused fitting outlet

pressure rating: the estimated maximum pressure a liquid can exert continuously inside the pipe at which the pipe won't fail

primer: a solvent used to soften joint surfaces prior to the application of solvent cement. it's usually tinted purple.

reducer coupling: a fitting that joins two pipes of different diameters to reduce the diameter of a pipe run


S - Z

sanitary fitting: a fitting that joins the assorted pipes in a drain / waste / vent system; designed to allow solid material to pass through without clogging

schedule: how thick the wall is for any size of pipe; the higher numbers mean a thicker wall (e.g., Schedule 80 is stronger than Schedule 40)

socket (slip): a female end or the hub of a fitting that fits over pipe

solvent cement: a mixture of solvents (chemicals) and plastic resins used to weld plastic pipe and fittings 

spigot: a male end of a fitting that's the same size as the pipe it's inserted to

standard dimension ratio (SDR) pipe: a type of pipe in which the dimension ratios are constant for any given class (unlike schedule pipe, where as the diameter increases the pressure rating remains constant for any given class of pipe)

static pressure: the pressure when no water is flowing

street elbow: a 90-degree fitting that has a male end on one side and female end on the other side

stress-crack: an external or internal crack in a plastic caused by tensile stresses less than its short-time mechanical strength

tailpiece: the section of drain fitting that protrudes into the trap

tee: any T-shaped plumbing fitting that diverts water to another line

thermal expansion: the increase in a length of a plastic part due to a change in temperature

thermoplastics: a group of plastics that can repeatedly be softened by heating and hardened by cooling

trap: a curved or V-shaped section of drain line that prevents sewer odors from escaping

weld line (knit line): a mark on a molded plastic part formed by the union of two or more streams of plastic flowing together

wye: a fitting with three openings used to create branch lines

Common Industry Abbreviations

ABS: acrylonitrile butadiene styrene

ASTM: American Society for Testing and Materials

C: compression

CPVC: chlorinated polyvinyl chloride

CTS: copper tube size

DWV: drain / waste / vent

FIP: female iron pipe

FPT: female pipe thread

H: hub

ID: inside diameter

IPS: iron pipe size

MIP: male iron pipe

MPT: male pipe thread

NPS: National Pipe Tapered Threads Standard

NSF: National Sanitation Foundation

OD: outside diameter

PSI: pounds per square inch

PVC: polyvinyl chloride

S: slip or socket

SP / SPG: spigot

1/4 bend: 90-degree bend

1/6 bend: 60-degree bend

1/8 bend: 45-degree bend

1/16 bend: 22-1/2-degree bend