What does the IPC require for a joint in hubless cast-iron soil pipe?
- AA hot-poured lead and oakum joint packed at every connection and caulked tight so the joint holds against head pressure during the drainage test
Lead and oakum is the traditional joint for hub-and-spigot cast iron, where a bell receives a spigot and gives the lead something to caulk against. Hubless pipe has plain ends and no bell, so there is nothing to pack.
- A shielded coupling with an elastomeric sleeve and stainless steel clamps, tightened to the torque specified by the coupling manufacturer
- CA solvent-cemented sleeve installed over the plain pipe ends, since the sleeve spans the gap and the cement seals it without any clamping
Solvent cement dissolves and refuses certain plastics into a single piece. It has no chemical action on iron at all, so a cemented sleeve on cast iron is only a loose cover sitting over an open joint.
- DA threaded coupling engaging not less than three full threads, which is the engagement accepted on threaded pipe joints
Three-thread engagement is a genuine figure from the joint provisions for threaded pipe, which is why it reads well. Cast-iron soil pipe is not threaded, and its wall was never intended to carry a thread.
Why B is correct
A hubless joint is a listed shielded coupling: an elastomeric gasket sleeve inside a stainless steel shield, clamped with worm-drive bands and tightened to the manufacturer's specified torque with a preset torque wrench. The coupling also carries no structural duty, so the piping has to be supported independently rather than letting the joints hold the weight of the run.
What this question is testing
This tests knowledge of the joining method that matches the pipe form, hubless versus hub-and-spigot, and awareness that the coupling is a torque-specified assembly rather than a hand-tight connection. It also touches the support relationship at hubless joints.
On the job
Torque wrenches on no-hub couplings are not optional on a commercial job; inspectors carry one and check random joints. Crews that run the clamps down with a nut driver either leave them loose or crush the shield. Support the pipe so the coupling is not a hanger, keep the pipe ends square and clean, and remember that a heavy vertical run needs support at the base so the stack is not hanging on gaskets.
Memory technique
No hub, no bell, no lead: sleeve, shield, and a torque wrench.
Exam tip
Match the joint to the pipe end: bells get caulked or gasketed, plain ends get shielded couplings.
Where to look it up
Chapter 7, joints for cast-iron soil pipe, plus the hanger and support provisions in Chapter 3 that address support at hubless joints. Coupling standards and support intervals differ between IPC and UPC, so confirm the code your state adopted.