As the name implies, this fitting device is "Y" shaped. The branch runs out from the run port at an angle other than 90 degree. It is a fitting with three openings and is used to create branch lines. A standard wye allows one pipe to be joined to another at a 45 degree angle.

Wyes are similar to tees except that the branch line is angled to reduce friction that could hamper the flow and that the connection is typically at a 45-degree angle rather than a 90-degree angle. If a branch turns out at the end to be perpendicular to the through line, the fitting becomes a "tee wye".

PVDF Corrosive Waste Piping Systems utilize wye fittings that feature smooth ID without any irregularities for uninterrupted flow path. These fittings should be able to withstand acids, bases, and solvents, flame-retardant systems withstand intermittent corrosive fluids up to high temperatures. Polypropylene and PVDF Double Wyes and Double Reducing Wyes come in various sizes and are largely used for this purpose.

A wye branch allows to split a branch line equally in two directions. The opening sizes can vary for different situations, for instance in situation where a large main line needs to be split into two smaller branches.

Economy wyes are often spot-welded together; industrial wyes have a continuous weld at each seam. A true Wye fitting is also engineered for closed system instrumentation pigging configurations or wherever a smooth pipe branch is required.

The end connections of a standard wye can be :