Trade Exam · Module 5
Leak Detection and Repair
Find the leak with the meter and a few valve closures before you open anything, repair it with a joining method the code allows for that material, then test it the way the code tests new work. This lesson covers visible and hidden leaks, slab leaks, repair methods by pipe material, and the 2025 California Plumbing Code test and joint rules behind them.
Key Takeaways
- A moving meter with every fixture off confirms a leak; closing the house valve, then the water heater cold supply, tells you whether it is in the service line, the cold side or the hot side.
- Warm spots on a slab floor point to a hot line; damp areas with no heat point to cold piping, drainage or outside water.
- Permanent repairs use a joint the CPC allows for that material; clamps and epoxy are stopgaps.
- Solder and flux on potable water piping may contain no more than 0.2 percent lead (CPC 604.2, 605.1.4); push fit fittings must comply with ASSE 1061 (CPC 605.1.3.3).
- Copper under a slab should be run without joints where possible; any joints there must be brazed with wrought copper fittings (CPC 609.3).
- Water piping tests at not less than working pressure with water, or at least 50 psi with air, for at least 15 minutes; plastic pipe is not air tested unless the PEX, PP or PE-RT manufacturer allows it (CPC 609.4).
- DWV tests use a 10 foot head of water or 5 psi of air for at least 15 minutes (CPC 712.2, 712.3).
- Repairing a leak without replacing or rearranging pipe is permit-exempt under CPC 104.2; replacing a defective section is new work.
Why This Matters
"Isolate leaks and damage" and "repair plumbing" are both listed under the Service, Repair, and Remodel section of the CSLB C-36 exam. On the job, the plumber who pinpoints a leak before opening walls saves the customer drywall, flooring and money.
Step 1: Confirm There Is a Leak
Meter check. Have the customer turn off everything that uses water, including irrigation, ice makers and softeners in regeneration. Watch the meter's leak indicator or the sweep hand. If it moves, water is leaving the system somewhere.
Other signs:
- A water bill that jumps without a change in use.
- The sound of running water with everything off.
- Stains, damp drywall, soft flooring, mold or a musty smell.
- Warm spots on a slab floor.
Would you pass the C-36 today?
Take the free 21-question practice test. About 10 minutes, no account needed. You get your score by section and see exactly where you are losing points.
Take the free testKeep reading — unlock the full lesson
You're reading a free preview. Get the complete lesson plus everything you need to pass the California C-36 exam:
- All in-depth lessons, exam prep and After the License
- 1,000+ practice questions
- AI tutor (100 messages included)
- 14+ hours of audio lessons
- Full-length practice exams
- Pass guarantee
Already have an account? Sign in
More lessons in Service, Repair, and Remodel
- 1The Troubleshooting Process
- 2Common Drain Problems
- 3Common Water Supply Problems
- 4Leak Detection and RepairYou are here
- 5Sewer Line Repair and Replacement
- 6Remodel and Retrofit Work
- 7Emergency Plumbing Response
- 8Fixture and Water Heater Replacement
- 9Retrofit Plumbing Systems
- 10Disposal of Plumbing Materials