Quick answer
Cast iron was the standard drain and sewer pipe in many US homes built before about the 1970s. It lasts decades but scales up inside, cracks and rusts through, especially along the bottom of horizontal runs. Signs are repeated slow drains and clogs, sewer smell, damp spots or rust stains along the pipe, and in slab homes, wet floors. A camera inspection shows whether a section can be replaced or the line lined; HomeServe puts cured-in-place lining at $90–$250 per foot. Call (888) 217-6781 to reach a plumbing company taking calls in your ZIP.
Follow the short menu, then your 5-digit ZIP. The line goes quiet for a few seconds while it connects; stay on. If it does not connect, call once more: companies taking calls change minute to minute.
Written & reviewed by Marcus ReedIICRC WRT
Reviewed November 4, 2026· Next review May 2027
Cast iron drain pipe is heavy, quiet and durable, and it was standard in many US homes built before about the 1970s. It does wear out. The inside builds up rough scale that catches debris, and the bottom of horizontal runs, where water always sits, rusts thin and cracks.
Warning Signs
| Sign | What it suggests |
|---|---|
| Same drain clogs again and again | Scale or a crack catching debris |
| Several drains slow | Scale in the main stack or building drain |
| Sewer smell near the pipe | Crack or a failed joint |
| Rust stains or damp spots along the pipe | Pipe rusting through |
| Flaking, bulging pipe in the basement | Advanced corrosion |
| Slab home: damp floor, cracks, smell | Under-slab drain failing |
The Camera Decides
A camera inspection run from a cleanout shows scale, cracks, holes and channeling along the bottom, and where they are. It turns a guess into one of these options:
- Descaling: a machine grinds the scale off the inside wall, restoring flow in a sound pipe.
- Section replacement: cut out a failed piece and replace it with PVC or ABS.
- Cured-in-place lining: a resin liner forms a new pipe inside the old; HomeServe puts it at $90–$250 per foot.
- Full replacement: for a line that is broken or collapsed; Bob Vila puts trenchless replacement at $60–$250 per foot.
Talk to a plumber about this
One call reaches a plumbing company taking calls in your ZIP.
Under a Slab
In slab homes, the building drain runs under the floor. Failure shows as damp spots, cracks or smell. Lining avoids breaking up floors where the pipe allows it. See slab leak detection for the supply-line equivalent.
Costs and Next Step
Pricing per method is in sewer line replacement cost. See sewer line repair.
The Call
Call for a camera inspection when the same drain keeps clogging, you see rust or damp spots along the pipe, or a slab floor is damp. (888) 217-6781 connects you to a plumbing company taking calls in your ZIP. Follow the short menu, enter your 5-digit ZIP and stay on while it connects; if it does not connect, call once more, because the companies taking calls change minute to minute.
Reading to confirm what you already suspect?
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Frequently Asked Questions
How long do cast iron drain pipes last?
Many last 50 years or more, but life depends on the soil, the water and what goes down the drains. Many homes from the mid-20th century are reaching that age.
What are the signs of cast iron pipe failure?
Recurring clogs, slow drains, sewer smell, rust stains or damp patches along the pipe, and in slab homes wet or cracked floors.
Can cast iron pipe be lined instead of replaced?
Often. A cured-in-place liner forms a new pipe inside the old one, if the line is still roughly round. HomeServe puts lining at $90–$250 per foot.
Sources
Methodology: How we source and verify data · Report an error
Disclaimer: HearthDry is an independent educational resource. This article is for informational purposes only and does not constitute professional, legal, or insurance advice. Consult licensed professionals before making decisions about your property or insurance claims.
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