In the Field · Part 4
Gas piping in practice: sizing, CSST bonding, the pressure test, appliance connectors and shutoffs, sediment traps, and seismic shutoff valves
Gas is the system where a plumber's mistake is not a callback. This lesson is the working rules a C-36 uses on every gas job: how to size a line by the longest-length method against the code tables, why every CSST installation must be bonded to the electrical grounding electrode system, the California pressure test (10 psi for at least 15 minutes, no perceptible drop), what an appliance connection must consist of and where the shutoff has to be, the sediment trap the inspector always looks for, and the seismic gas shutoff valve that Los Angeles requires on sale and on alterations over $10,000, which is a permit item a plumber can sell honestly and install correctly.
What the full lesson covers
- Size gas piping by the longest-length method (CPC 1215.1.1): total the appliance inputs, find the longest run from the meter to the farthest outlet, and size every section from that length in Table 1215.2 for the pipe material and pressure. Undersized gas is a low-fire complaint on the day the heater and the furnace run together.
- CSST, and any system with a single segment of CSST, must be bonded to the electrical service grounding electrode system with a jumper on a fitting (1211.2). Lightning finds the unbonded run.
- The test: air, CO2, or nitrogen at not less than 10 psi, held at least 15 minutes with no perceptible drop, gauge on, inspector able to see it (1213.3). Never test with gas.
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More lessons in The Field: Method, Code, and Cases
- 1The diagnostic method: verify, isolate, cheapest test first, cause not symptom, the options ladder, document
- 2Permits: when one is required, what is exempt, pulling it online, the inspection sequence, what inspectors look for, and handling corrections
- 3Daily-use code: drainage slope, venting, water sizing, cleanouts, trap arms, and fixture units, with the section for each
- 4Gas piping in practice: sizing, CSST bonding, the pressure test, appliance connectors and shutoffs, sediment traps, and seismic shutoff valvesYou are here
- 5