Replacing old cast iron drain lines in San Jose homes
Cast iron drains rust from the inside, and by the time they leak the pipe around the leak is usually thin too.
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Perfect Tankless Plumbing, San Jose, CA
Cast iron drain-waste-vent systems in San Jose homes fail at roughly 50 years as they rust from the inside and crack along the bottom; replacement means cutting out the cast iron and installing ABS or PVC with correct slope and long-sweep fittings, which San Jose inspectors check at rough-in.
Updated September 2026
Drains & Sewer
How cast iron drains fail
Cast iron corrodes from the inside where waste flows. Scale builds up and narrows the pipe, the bottom of horizontal runs thins and cracks, and hub joints loosen. The symptoms are slow drains that do not respond to cleaning, sewer odor, and eventually leaks.
A camera shows how far it has gone. Replacement can be partial, the worst sections only, or full, the whole under-floor system, depending on what the footage shows.
Cost factors
What cast iron replacement costs
The published range below is for replacing a cast iron system in San Jose; slab or crawl space access is the biggest variable.
- Cast iron DWV replacement$6,500 to $16,000. Planning range from plumbingpriceguide.com, not our quote.
- Permit fees (San Jose)$350 to $800 for sewer, repipe or water heater permits. Planning range from proplumbersanjose.com, not our quote.
- Slab or crawl space. trenching concrete costs far more
- Partial or full. how much of the system is replaced
- Flooring. lifted and restored along trench routes
- Stack access. walls opened for vertical stacks
- Permit and inspection. rough-in inspected before closing
- Connection to the lateral. condition at the house cleanout
Options
Partial or full replacement
| Partial | Full | |
|---|---|---|
| Pipe replaced | Worst sections | Entire under-floor system |
| Cost today | Lower | Higher |
| Future failures | Likely elsewhere | Unlikely soon |
| Disruption | Localized | Wider |
| Best when | One defect, rest fair | Failure throughout |
| Camera evidence | Isolated damage | Scale and cracks everywhere |
Under-slab DWV
In slab houses, the main drain and branches run beneath the concrete. Replacing them means cutting trenches in the slab, removing the cast iron, laying new ABS or PVC on proper bedding and slope, passing inspection, and patching the concrete. Flooring along the trench route has to come up. Where only one branch has failed, a partial replacement or a lining may avoid opening much of the floor, and the camera footage tells us which approach the pipe will actually support before anyone starts cutting concrete.
Crawl space DWV
In raised-floor houses, drains hang in the crawl space where they can be reached and replaced without breaking floors. We support the stack, cut out the cast iron in manageable sections, and install new pipe with proper hangers and slope. Transitions to remaining cast iron use shielded couplings. Crawl space replacement is usually the less disruptive version of this job, and it is a good time to replace old galvanized supply lines running alongside, since the crawl space is already open and the crew is already under the house.
Partial vs full replacement
If the camera shows one cracked section with the rest in fair condition, partial replacement is reasonable. If scale, thinning and cracks appear throughout, patching one area moves the next failure a few feet along the pipe. We show you the footage and give you both options with the trade-offs. Full replacement costs more today and ends the cycle; partial replacement costs less now and leaves the rest of the aging system in place to fail on its own schedule, which is a reasonable choice when a remodel or sale is already planned.
Local context
Cast iron age and San Jose drain inspections
Published San Jose plumbing guidance puts the working life of cast iron drain-waste-vent systems at roughly 50 years, which covers a large share of the city's housing. When those drains are replaced, California Plumbing Code 706.3 requires long-sweep fittings where horizontal drains change direction, and San Jose inspectors verify it at rough-in. We lay out the new drains with those fittings from the start so the inspection is a formality rather than a redesign.
How the job runs
How a cast iron replacement runs
- 1
Camera the system
Find the failing sections.
- 2
Choose the scope
Partial or full, with footage.
- 3
Permit
Filed before work starts.
- 4
Remove the cast iron
Supported and cut in sections.
- 5
Install new drains
Correct slope and long-sweep fittings.
- 6
Inspect and restore
Rough-in inspection, then close up.
Timing
How long the house is without drains
Crawl space replacements are often finished in one to three days, with drains usable again in the evenings in many cases.
Slab replacements take longer because of cutting, inspection and concrete patching, and we plan temporary drain use with you before starting.
FAQ
Cast Iron Drain Line Replacement questions from San Jose homeowners
Published San Jose guidance puts it at roughly 50 years before failures become common.
Sometimes, when the pipe still holds its shape. Badly cracked or collapsed sections need replacement.
ABS or PVC drain pipe, laid with correct slope and long-sweep fittings.
Plastic drains can be louder where water falls through a wall. Insulation around stacks helps.
Yes. Drain replacement is permitted and the rough-in is inspected.
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One number, any hour
Plan your drain replacement
Call to book a camera inspection. We will show you what the cast iron looks like inside.
