A waste pipe carries used water from basins, baths, showers, kitchen sinks, washing machines and dishwashers to either the soil stack or directly to a gully outside the property. Common UK diameters are 32mm for basins, 40mm for sinks and showers and 50mm for some commercial appliances, in line with Building Regulations Part H1. Waste pipes are usually made of PVC-U or polypropylene and connect via compression or push-fit fittings. A trap must always be installed close to the fitting to maintain a water seal that prevents drain odours entering the room. Branches must be laid to a suitable gradient, generally between 18mm and 45mm per metre, to keep flows moving without causing siphonage of the trap seal.
Waste pipe
Smaller diameter pipe carrying water from sinks, baths and basins to the drainage system.
