Trade Exam · Module 3
Fuel Gas Piping
Fuel gas piping under Chapter 12 of the 2025 California Plumbing Code: approved and prohibited materials, the 5 psi limit inside buildings, plastic pipe outdoors and underground only with listed transition fittings and a tracer wire, cover depth, support spacing, CSST bonding, the appliance shutoff within 6 feet with a union after it, where a sediment trap is and is not required, and the 10 psi, 60 psi and 30 psi pressure tests.
Key Takeaways
- Size gas piping for the sum of the maximum input of all appliances served (1208.3.1), using the Chapter 12 sizing methods and tables (1215).
- PVC, CPVC and cast iron may not be used for gas. Steel pipe is at least Schedule 40. Copper tubing is Type K or L (1208.5).
- Plastic gas pipe is installed outdoors, underground only, with listed transition fittings and an electrically continuous tracer (1210.1.7).
- Underground gas piping gets at least 12 in of cover, 18 in where external damage is likely; otherwise it goes in conduit (1210.1.1).
- Each appliance has an accessible shutoff valve within 6 ft, upstream of any connector, with a union or flange downstream (1212.6).
- A sediment trap goes downstream of the shutoff, close to the appliance inlet; ranges, clothes dryers, illuminating, decorative, gas fireplace and outdoor cooking appliances are exempt (1212.9).
- Test at not less than 10 psi for at least 15 minutes; welded piping or gas over 14 in water column 60 psi for 30 minutes; CSST over 14 in water column 30 psi for 30 minutes. Never oxygen (1213.1.6, 1213.3).
Why This Matters
The CSLB C-36 study guide lists fuel gas piping as one of the four content areas of Underground and Rough Systems, the section weighted at 22 percent of the trade exam. The rules live in Chapter 12 of the 2025 California Plumbing Code (CPC), much of it drawn from NFPA 54. The stakes are high: a leak or a bad connection can cause a fire or an explosion. This lesson covers the piping from the point of delivery to the appliance connection.
Inspection Comes Before Gas
- Excavations (1203.2): trenches for underground gas piping stay open until the piping is inspected and approved. If it is covered first, the AHJ can order it exposed.
- Rough piping inspection (1203.3.1): after the piping is installed and before it is covered or concealed or any appliance is attached. The inspector checks size, material and installation.
- Final piping inspection (1203.3.2): after concealed portions are closed in and before any fixture, appliance or shutoff valve is attached.
- No gas without the certificate (1204.3): it is unlawful for the gas supplier to turn on gas or a meter until the certificate of final inspection has been issued.
- Cap every outlet (1210.8.1): each outlet, including a valve, is closed gastight with a threaded plug or cap right after installation and left closed until the appliance is connected.
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