Cast Iron Sewer Pipe Replacement Cost

Cast iron sewer pipe is strong, quiet, and prone to rust from the inside. Replacing it costs the same installed rates as any other lateral on the sewer line replacement cost guide. The material price is a separate, much smaller number. Do not confuse the two.

Installed cost, not material cost

Published job totals run $7,500–$30,000 for digging and $4,000–$20,000 for trenchless methods. The per-foot page shows the multiplication. The trenchless cost page adds restoration comparisons.

Cast iron's published life is 50–75 years. PVC's is 50–100+ years. Life is not a deadline. A 50–75 years rating does not mean your pipe fails on a birthday. It means you should look, not guess.

Signs the iron is failing

Rust inside the pipe can create scale, slow drains, and eventual holes. You might see more than one slow fixture, gurgling, a sewage smell, or a damp strip of yard. Those signs are listed on the damage signs page. They overlap with clay and Orangeburg problems. The material is confirmed on camera, or when a piece is actually exposed.

Orangeburg pipe is a different failure. It flattens. Cast iron tends to rust and scale. Both can end in a replacement. The camera tells you which story you are in.

PVC vs cast iron on the way back

When the line is dug and replaced, most new laterals go in as PVC because it resists corrosion. (Pipe bursting usually pulls in HDPE (high-density polyethylene) instead.) The material gap is large: about $3–$8 per foot for PVC versus about $20–$75 for cast iron. The installed job dwarfs both. Choosing PVC does not cut a $150 bursting rate down to the PVC material price.

If the iron is mostly intact, CIPP lining can rebuild the inside at $135–$150 per foot. CIPP is a resin liner cured in place. It needs a round host. Heavy rust that has opened or collapsed the pipe pushes you to bursting or a dig. A belly, a sag that holds waste, also pushes you to a dig if the slope must change.

Worked example

Older homes in the Northeast often still have cast iron laterals. Take a 75-foot line on a suburban lot where the iron is scaled but still round enough to line.

Material only, for the same length: 75 × $20 = $1,500 on the low end and 75 × $75 = $5,625 on the high end.

Installed lining pipe work is $10,125–$11,250, already far above the material-only figure. With an inspection, a permit, and the Northeast factor of ×1.15–×1.30, the rounded total is $11,900–$16,600.

If someone quotes you the material price as the job price, the quote is missing the crew, the pits or the trench, the permit, and the restoration.

How to save money

• Confirm cast iron on camera before you accept a full replacement.
• Ask whether the iron is still round enough to line.
• Compare a PVC replacement bid with a lining bid only if lining fits.
• Do not add material prices on top of an installed per-foot rate.
• Get the restoration line in writing if the crew will dig.