Plumbing Fittings (Couplings, Reducers, Wyes and U-Bends)

The Full Picture

A fitting is any part that connects, redirects, branches or resizes pipe. The main types are couplings, elbows, tees, wyes, reducers, adapters, unions, caps and plugs, and bends. A coupling joins two pipe ends of the same size. A reducer, sometimes written as a reducing coupling or a reducer bushing, joins two different sizes. A wye is a Y-shaped fitting that brings a branch into a main at an angle (commonly 45 degrees), which lets drain flow turn smoothly, and a wye with a 45-degree bend added is often called a combination or combo. A U-bend, also called a return bend, turns the pipe through 180 degrees, and the trap under a sink is one form of it. Drain and vent systems use long-turn and 45-degree patterns so solids do not catch, while pressure supply systems use tight elbows and tees.

Fittings differ by system and material. Drain fittings are of the drain pattern, with a smooth interior and a slope built into branches. Supply fittings for copper, PEX or CPVC are pressure fittings with different joints (solder, crimp, press, solvent). Fittings must match the pipe material and size, which is why a fitting count is always listed by type, size and material, for example "3-in x 2-in ABS wye" or "3/4-in copper 90." The spec section for the pipe sets the material and the joint method, and the plumbing code lists which fittings are approved for which service.

Fittings are counted from the plumbing plans, riser diagrams and isometrics, where each change of direction, branch, size change and connection to a fixture or equipment is visible. Plan views often show pipe as simple lines, so the estimator must infer fittings from the geometry: a turn is an elbow, a connection to a main is a tee or wye, and a change in line size is a reducer. An isometric makes this easier because every fitting is drawn. The unit is each, by size and type, with reducing fittings stated by both sizes (a 4 x 4 x 2 wye has a 2-in branch).

A shortcut used in early estimates is a fittings-to-pipe ratio, such as an assumed number of fittings per 100 LF of pipe, or fittings priced as a percentage of the pipe cost. Those ratios vary a lot between a simple DWV run and a congested mechanical room, so they suit budget stage only and should be replaced by counted fittings when the drawings allow. Common mistakes include leaving out couplings between pipe lengths (a run of N sticks needs N - 1 couplings), mixing up reducing and straight fittings, missing cleanout adapters, and forgetting that a larger or special-material fitting costs far more than a small one.