# What is a breeches piece?
**A breeches piece (Dutch: broekstuk) is a Y-shaped pipe fitting used in drainage and plumbing systems to connect a branch pipe to a main pipe. The fitting resembles a pair of trousers — hence the name — with two inlet legs merging into a single outlet.**
## How a breeches piece works
The fitting allows two separate drain lines to merge into one larger pipe while maintaining smooth flow. The branch typically enters the main pipe at an angle (usually 45 or 60 degrees) rather than at a sharp 90-degree turn. This angled connection reduces turbulence, prevents blockages, and ensures wastewater flows efficiently toward the main sewer.
### Key characteristics
– **Y-shaped geometry:** Two inlets converge into one outlet.
– **Angled junction:** Typically 45 or 60 degrees to promote laminar flow.
– **Available in various materials:** PVC, cast iron, clay, and stainless steel.
– **Multiple diameter combinations:** Branch pipes are often smaller than the main pipe.
## Design considerations
When specifying a breeches piece, engineers consider the pipe diameters, the junction angle, the expected flow rates, and the material compatibility with the rest of the system. Incorrect sizing can cause backflow or pressure surges. Building codes typically dictate the minimum angles and maximum flow velocities at junctions.
## Applications
– Below-ground foul drainage systems
– Rainwater drainage combining roof outlets
– Soil stacks in multi-storey buildings
– Industrial wastewater collection networks
– Combined sewer connections
## Related terms
– Branch pipe
– Main drain
– Junction fitting
– Soil stack
– Inspection chamber
– Trap
– Fall (gradient)
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