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Cast iron drain replacement in San Jose, under the house or under the slab
Drains that never quite clear, a sewer smell under the house, a rust stain or a crack along the bottom of an old black pipe. Cast iron drain lines from the 1950s to the 1970s are reaching the end, and we replace them with ABS or PVC, a section at a time or all at once.
Cast iron drain pipe replacement in San Jose swaps corroded or cracked cast iron drain, waste and vent lines for ABS or PVC. Pipe in a crawl space is replaced from below; lines under a slab need the floor opened, a reroute or a lining option. A camera inspection first shows whether sections or the whole system have failed.
The job
How cast iron fails
Cast iron drains corrode from both sides: sewer gases eat the inside from the top down, while moisture and soil work on the outside. The bottom of horizontal runs thins first, often cracking along its length. Scale builds inside and catches waste, so drains slow even after cleaning. By the time a stain or smell appears, the pipe has usually been failing for years.
Jetting can restore flow in scaled but sound cast iron; see hydro jetting. The lateral outside the house is a separate job, covered under sewer line replacement.
Cost factors
What changes the price of cast iron replacement
Planning range, not a quote: $6,500 to $16,000 on a 2,000 sq ft footprint (ABS or PVC inside conditioned space). Source: plumbingpriceguide.com, 2026-05-26.
- Extent One section or the whole system.
- Location A crawl space is simpler than under a slab.
- Walls opened Vent stacks and wall lines need access.
- Fixture tie-ins Each fixture reconnection adds work.
- Permit Drain replacement is permitted work.
Every job is priced after we see it; any published range is for planning only.
Under-house cast iron to ABS
On raised-foundation homes, the drain lines run through the crawl space, where they can be reached from below. We cut out the cast iron in sections, support the remaining pipe as we go, and replace it with ABS or PVC at the correct slope on new hangers. Connections to fixtures above are made from below where possible, so walls stay closed. A crawl-space replacement is one of the less disruptive big plumbing jobs, and the difference shows right away in how fast the drains run.
Kitchen drain line under the slab
Kitchen lines carry grease that settles in cast iron's rough interior, and under a slab they are the hardest line to reach. When the camera shows the kitchen branch cracked or heavily scaled, the options are opening the floor along the run, rerouting a new drain through a wall or crawl space where the layout allows, or lining the old pipe if it is still round. We show you the footage and price each workable option, because the right choice depends on what sits on top of that floor.
Vent stack replacement
The vent stack runs up through the house to the roof and lets the drains breathe. Cast iron vents rust through at joints and where they pass through the roof, and a failed vent shows up as gurgling drains, slow flow and sewer smell indoors. Replacing the stack means opening walls along its path, so it is often combined with a remodel. We replace it with ABS or PVC, reflash the roof penetration with a new boot, and test the whole system before walls close.
Partial replacement of a rotted section
Not every cast iron system needs replacing at once. If the camera shows one rotted section in otherwise serviceable pipe, we cut out that length and join new pipe to the old with shielded no-hub couplings, at a fraction of the cost of a full replacement. The honest caveat is that the remaining cast iron is the same age, so we tell you what we saw on the rest of the run and how it looks, and you decide whether to replace more while the access is open.
What is included
What a cast iron replacement includes
- Camera inspection of the drain system
- Scope and method in writing
- Plumbing permit
- Old cast iron cut out and removed
- New ABS or PVC at proper slope
- Hangers and supports replaced
- Shielded couplings at every transition
- Water test before closing
- Inspection and cleanup
What happens after you call
How a cast iron replacement runs
- 1
Camera
The system recorded end to end.
- 2
Scope
Sections or full system, in writing.
- 3
Permit
Pulled before work starts.
- 4
Replace
Cast iron out, ABS or PVC in.
- 5
Test
Water test before closing.
- 6
Inspect
City inspection and cleanup.
Local context
San Jose cast iron at 50 to 65 years
Houses built in San Jose before the mid-1970s were typically fitted with cast iron hub-and-spigot drain, waste and vent systems, and that pipe tends to fail somewhere between 50 and 65 years in service. Most of it is inside that window now. The usual failure points match the age: thinned bottoms on the horizontal runs under the house, and cracked joints where the stack turns toward the building drain.
Timing
How long the house is without drains
Crawl-space replacements can often be sequenced so part of the house keeps draining while another section is replaced. Slab work takes the affected line out of service until the new pipe is in and tested. You get the expected downtime in writing, and we plan the work so at least one toilet stays usable whenever the layout allows.
FAQ
Cast iron drain questions
Slow drains, sewer smells, rust stains or cracks; the camera confirms it.
Single rotted sections can be; widespread thinning means replacement.
ABS or PVC at the correct slope, with new supports.
They can be; we can insulate lines near bedrooms.
For vent stacks, yes; crawl-space lines are reached from below.
Sometimes, if the pipe is still round; the camera decides.
Yes. Drain replacement is permitted and inspected.
Related work
Other Drains & Sewer jobs we handle
Get your cast iron drains checked in San Jose
Call any hour to book a camera inspection of the system.
Updated September 2026