Cast Iron Drain Pipe Replacement Cost
Replacing cast iron drain pipe runs $75 – $250 per linear foot. A whole-house job, the vertical stack plus the horizontal branches, lands at $5,000 – $20,000. Under-slab cast iron is the expensive case because the floor has to come up. Lining can be an alternative when the pipe is not fully channeled out.
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| Scope | Range | Note |
|---|---|---|
| Per linear foot (accessible) | $75 – $250 / ft | Basement, crawl space, or open wall |
| Single stack replacement | $2,000 – $6,000 | One vertical run, floor to roof vent |
| Whole-house stack + horizontals | $5,000 – $20,000 | All drain, waste, and vent piping |
| Under-slab cast iron | $150 – $250 / ft | Concrete cut, removed, and re-poured |
| Factor | Effect | Why |
|---|---|---|
| Under-slab location | highest cost | Demolition and re-pour on top of pipe work |
| Finished walls and ceilings | + drywall repair | Open and patch to reach the pipe |
| Asbestos / lead investigation | + $300 – $1,500 | Older homes may need testing |
| Lining instead of replacing | $80 – $250 / ft | Avoids demolition where pipe allows |
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Why cast iron fails, and how it shows up
Cast iron drain pipe has a 50 to 75 year lifespan, and most homes that still have it are now inside that window. It fails from the inside out. Decades of waste flow corrode the bottom of horizontal runs, a process called channeling, where the pipe wears into a trough and eventually a hole along the bottom. Scaling is the other mode: mineral and rust buildup that narrows the bore until the drain chokes and backs up.
The symptoms are recurring slow drains, backups that return after cleaning, sewer odor from cracks, and stained or damp spots on ceilings below the pipe. A camera inspection is the clearest diagnosis: the footage shows the rusted, channeled, or scaled interior directly, and tells you whether the pipe is a candidate for lining or past saving.
What replacement actually costs
Accessible cast iron, in a basement, crawl space, or an open wall, runs $75 – $250 per foot to replace with PVC or ABS. A single vertical soil stack from the basement to the roof vent lands at $2,000 – $6,000. A whole-house job that swaps the stack and all the horizontal branches runs $5,000 – $20,000, with the spread set by home size, how many bathrooms, and how much wall and ceiling has to be opened and patched.
The number climbs fast when finished surfaces are involved. Replacing pipe behind tiled walls or above finished ceilings adds demolition and restoration on top of the plumbing. For a whole-house repipe of supply lines as well, the scope and cost expand further, which our broader pipe guides cover.
Under-slab cast iron: the expensive case
The worst-case location is the drain line buried in the concrete slab under the house. Reaching it means jackhammering the floor, excavating the trench under the foundation, replacing the pipe, backfilling, and re-pouring the slab, often inside finished living space. That demolition-and-restoration overhead is why under-slab work runs at the top of the per-foot range, $150 – $250, and why a modest length of pipe can become a five-figure project.
This is exactly where trenchless lining earns its keep. If the under-slab cast iron is corroded but not fully collapsed or channeled through, CIPP lining can rebuild the pipe from the inside without opening the floor, often at a fraction of the demolition cost. A camera inspection decides it: a pipe with enough structure left to host a liner is a lining candidate; one channeled into open trough is a dig.
Lining as an alternative to replacement
Replacing cast iron is not the only path. Where the pipe still holds its shape, an epoxy liner cured inside it gives a new, corrosion-proof, jointless interior with a long service life and no demolition. For accessible runs the savings are real; for under-slab runs they can be dramatic, since lining skips the concrete work entirely.
The limits are the same as any lining job. A pipe channeled into an open trough at the bottom, or one that has collapsed, cannot be lined and must be replaced. The honest sequence is a camera scope first, then a plumber who tells you which sections can be lined and which have to come out, rather than defaulting to a full tear-out or overselling a liner that will not seat.
A note on Orangeburg pipe
If your home was built or had sewer work between the 1940s and 1970s, the buried sewer lateral may be Orangeburg, not cast iron. Orangeburg is a pipe made of wood pulp and tar, lightweight and cheap in its day, and it fails differently: it absorbs moisture, softens, and deforms oval before collapsing, often within 30 to 50 years.
Orangeburg cannot be reliably lined once it has gone soft and lost its round shape, since there is no rigid host to support a liner. The standard remedy is replacement, either by open trench or by pipe bursting, which threads new pipe through while breaking the old line out. A camera scope identifies Orangeburg quickly by its dark, fibrous, often deformed wall, and turns a mystery backup into a clear plan.
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