Trade Exam · Module 5
Sewer Line Repair and Replacement
When every drain in a building backs up, the problem is usually in the building sewer. This lesson covers how to diagnose it with a cleanout and a camera, the repair options from clearing to trenchless lining to full replacement, and the 2025 California Plumbing Code rules on sewer materials, slope, cleanouts, clearances, trenchless methods and testing, plus the 811 notice and trench safety rules that apply when you dig.
Key Takeaways
- The building sewer begins 2 feet outside the building wall (CPC 715.1); a problem affecting every fixture usually lives here or in the building drain.
- Camera the line before recommending spot repair, lining or replacement; clearing a stoppage is permit-exempt, replacing pipe is new work (CPC 104.2).
- Building sewers slope at least 1/4 inch per foot; with AHJ approval where impractical, 4 to 6 inch pipe may go to 1/8 inch per foot and 8 inch and larger to 1/16 inch per foot (CPC 718.1).
- Approved building sewer materials are in Table 701.2, including PVC, ABS, cast iron, PVC sewer pipe to ASTM D3034, polyethylene and extra strength vitrified clay; no building sewer may be smaller than the building drain (CPC 717.1).
- Trenchless lining and pipe bursting are allowed where the AHJ permits, to the ASTM standards in CPC 715.3.
- Keep the minimum distances in Table 721.1: 2 feet from buildings, 50 feet from water supply wells, 10 feet from a parallel public water main.
- Building sewers are tested by filling with water or an approved low pressure air test; plastic is not air tested (CPC 723.1).
- Delineate the dig area and notify 811 at least two working days, and not more than 14 calendar days, before excavating (Gov. Code 4216.2); trenches 5 feet or deeper need a protective system (8 CCR 1541.1).
Why This Matters
Sewer work touches three of the five C-36 exam sections: Underground and Rough Systems (excavation and underground installations), Service, Repair, and Remodel (troubleshoot, isolate damage, repair), and Safety. CSLB's C-36 study guide also lists California Government Code 4216, the Underground Service Alert law, as a reference.
Where the Building Sewer Starts
The CPC defines the building drain as the lowest piping of the drainage system that receives the discharge from soil, waste and other drainage pipes inside the walls of the building and carries it to the building sewer, which begins 2 feet outside the building wall. The building sewer carries it on to the public sewer, private sewer or private sewage disposal system. Under CPC 715.1, from 2 feet outside the building the building sewer must be of the materials the code prescribes for building sewers.
Knowing the boundary matters because the rules for materials, slope, cleanouts and testing are written separately for building drains and building sewers.
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More lessons in Service, Repair, and Remodel
- 1The Troubleshooting Process
- 2Common Drain Problems
- 3Common Water Supply Problems
- 4Leak Detection and Repair
- 5Sewer Line Repair and ReplacementYou are here
- 6Remodel and Retrofit Work
- 7Emergency Plumbing Response
- 8Fixture and Water Heater Replacement
- 9Retrofit Plumbing Systems
- 10Disposal of Plumbing Materials