A soil pipe is a vertical pipe, typically 100mm diameter, that carries waste from toilets and other foul fittings down to the underground drain. It is normally installed externally on older UK properties and internally within boxed-in shafts in modern construction. The pipe must be ventilated to the open air, either by extending above the roof line or by fitting an air admittance valve, to prevent traps being drawn out by negative pressure. Cast iron was the traditional material in Victorian London terraces, but PVC-U and HDPE are now standard for new installations. Soil pipes are required by Building Regulations Part H to have rodding access and to be of appropriate diameter for the connected appliances. Internal soil pipes are usually fitted with acoustic sleeves to reduce noise transmission between flats.
Soil pipe
Vertical pipe carrying foul wastewater from toilets and waste fittings down to the drain.
