Glossary
Cast Iron Pipe
Heavy, brittle pipe made from molten iron, commonly used for drain, waste, vent, and water lines in older buildings.
Cast iron pipe is manufactured by pouring molten iron into molds, producing thick-walled tube with bell-and-spigot or no-hub couplings. It's strong under compression, resists corrosion better than mild steel, and handles high temperatures without degrading, making it standard for DWV systems in commercial buildings and older residential work from the 1800s through the 1980s.
In the field, cast iron requires respect. It's brittle and breaks under impact or torsional stress—dropping it or overtightening a coupling can crack it. Cutting requires a snap cutter, hacksaw, or reciprocating saw with a metal blade; angle grinders scatter sparks and create dust hazards. Joints use oakum and lead (sealed with a caulking tool) on older bell-and-spigot pipe, or rubber no-hub bands on modern no-hub cast iron.
Old cast iron clogs easily because the interior surface roughens with age and mineral deposits. You'll encounter it constantly in renovation work, storm and sanitary lines, and high-rise buildings. It lasts 50+ years but fails internally—scale buildup, root penetration, or casting defects—forcing replacement with PVC or ABS. Know your local codes: some jurisdictions still require cast iron for certain commercial applications, and mixing materials in a run demands proper transition fittings.