A strap-on boss is a retrofit branch fitting clamped onto an existing soil pipe to add a new waste connection point without replacing the whole stack. UK installations follow BS EN 1329 and BS EN 1519 and require a hole to be cut into the host pipe before the boss is fitted with rubber gaskets and stainless steel straps. Strap-on bosses are commonly used during bathroom refurbishment in London flats where a new fitting needs to be added to an existing PVC-U or cast iron soil stack. Connections are typically made for 32mm, 40mm or 50mm waste pipework. Care is needed to position the cut accurately and to seal the joint cleanly, particularly on cast iron pipes where the surface may be uneven. Periodic inspection is good practice to confirm long-term reliability.
Strap-on boss
Retrofit fitting clamped onto a soil pipe to add a new waste connection point.
