A soil pipe boss is a branch fitting on a soil stack that accepts a waste pipe connection from a basin, bath, sink or shower. UK soil systems use moulded bosses on PVC-U and HDPE stacks, sized to suit 32mm, 40mm and 50mm waste pipe in line with BS EN 1329 and BS EN 1519. Single, twin and multi-port bosses allow several wastes to enter at the same level. The boss connection must be at the correct distance below the trap to comply with Building Regulations Part H1 and avoid siphonage. Strap-on bosses can be added retrospectively to existing soil stacks during bathroom refurbishment, providing a useful option for London flats where the stack runs through stud walls or service ducts.
Soil pipe boss
Branch fitting on a soil pipe that accepts a waste connection from a basin, bath or sink.
