Trade Exam · Module 3
Testing and Inspection
The inspection and test steps the 2025 California Plumbing Code sets before plumbing can be covered or used: underground, rough-in and final inspections, uncovering work that was hidden too soon, the drain and vent water test (10 foot head for 15 minutes) and air test (5 psi for 15 minutes, never on plastic), the building sewer test, the water supply test (working pressure or 50 psi air for 15 minutes), the fuel gas tests (10 psi for 15 minutes, 60 psi or 30 psi for 30 minutes), and the gauge rules.
Key Takeaways
- Nothing is covered, concealed or put into use until it has been tested, inspected and accepted (105.2.1.2). Hidden work can be ordered uncovered (105.2.1).
- Tests are made in the presence of the AHJ (105.3), and the permit holder must be sure the work will pass before calling for inspection (105.2.5).
- DWV water test: no section tested with less than a 10 ft head, held at least 15 minutes, tight at all points (712.2).
- DWV air test: 5 psi or 10 in of mercury, held at least 15 minutes without adding air (712.3). Plastic pipe is never air tested (712.1).
- Water supply: water at or above working pressure, or air at least 50 psi (not on plastic), for at least 15 minutes without leaks (609.4).
- Fuel gas: at least 10 psi for at least 15 minutes; 60 psi for 30 minutes for welded piping or gas over 14 in water column; 30 psi for 30 minutes for CSST over 14 in water column; never oxygen (1213.1.6, 1213.3).
- Gauges: tests of 10 psi or less use gauges in 0.10 psi increments or finer, over 10 to 100 psi in 1 psi increments or finer, and the gauge range may not exceed twice the test pressure (318).
Why This Matters
The CSLB C-36 study guide lists "insulation and system testing" as one of the content areas of Underground and Rough Systems, the section weighted at 22 percent of the trade exam, and it lists "job site inspections" under Planning and Estimating. In the field, a missed test or an early cover-up is one of the most expensive mistakes a plumbing contractor can make, because the fix means tearing out finished work.
Every test value in this lesson comes from the 2025 California Plumbing Code (CPC). Notice that none of them is "a small drop is okay." The code's pass standard is tight, no leaks.
The Inspection Sequence
Chapter 1, Division II of the CPC is the administrative chapter. State agencies adopt it only as shown in the adoption matrix, and each local building department runs its own inspection program, so always confirm the steps with your AHJ. The model sequence in 105.2 is:
- Underground inspection: after trenches are excavated and bedded and the piping is installed, before backfill is placed.
- Rough-in inspection: before wall or ceiling membranes are installed.
- Final inspection: when the installation is complete.
Supporting rules:
- Scheduling (105.2.3, 105.2.4): the person doing the work notifies the AHJ that it is ready; the model text calls for notice at least 24 hours ahead, and the AHJ may require the request 1 working day in advance.
- Be ready (105.2.5): the permit holder must make sure the work will stand the required test before calling for inspection.
- Witnessed tests (105.3): tests are conducted in the presence of the AHJ or its appointed representative.
- Failed work (105.3.2): make the corrections and resubmit for test or inspection.
- Approval (105.3.3): when the work passes, the AHJ issues a certificate of approval to the permittee on demand.
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