A branch drain is a subsidiary section of pipework that links a single appliance or group of nearby fittings to the main drain run. Typical branches serve washing machines, dishwashers, kitchen sinks, basins and baths, joining a soil pipe or larger collector via a swept junction. UK Building Regulations Part H limits the permissible length and gradient of branch drains so that water seals in traps are protected against siphonage and back-pressure. Where a branch exceeds these limits, an anti-siphon trap or air admittance valve is usually required. Blockages on branch drains are often localised and present as slow drainage at a single fitting rather than affecting the whole property. Access points such as rodding eyes are normally provided so that engineers can clear branches without disturbing the main run.
Branch drain
Smaller drain pipe connecting an individual appliance or fixture to the main drain run.
