In the Field · Part 4
Water heaters I: tank. Seismic strapping, the T&P discharge line, expansion tanks, sediment traps, pans, venting, and the garage rules
The tank water heater is the job a residential plumber does most and the job that fails inspection most, for the same six reasons every time. This lesson is those six items with the code section and the exact requirement for each: the two seismic straps and where they go, the T&P discharge line and its eight rules, the expansion tank that a regulator or check valve makes mandatory, the sediment trap, the drain pan and when it is required, and the garage rules for ignition height and vehicle protection. It closes with the replacement sequence as an inspector would check it and with the case in lesson 4.20, where a heater failed twice on items that were on this page.
What the full lesson covers
- Two straps, one in the upper third and one in the lower third of the tank, the lower one at least 4 inches above the controls, anchored to the structure (CPC 507.2; Health and Safety Code 19211 makes it apply to every existing residential heater too).
- The T&P discharge line: full size of the valve outlet, no valves, downward, by gravity, through an air gap to the drain or outside ending 6 inches to 2 feet above grade, not trapped, not threaded at the end, never into the pan (608.5).
- An expansion tank is required whenever a check valve, backflow preventer, or pressure regulator prevents expansion back into the main, on the building side of that device, sized and secured (608.3). Most houses with a regulator need one, and most old installations do not have one.
- Sediment trap on the gas line downstream of the shutoff, oriented so the capped nipple hangs below the run (1212.9); drain pan with a 3/4-inch drain to a visible termination where the heater is in an attic or over finished space (507.5).
- In a garage, the ignition source sits at least 18 inches above the floor unless the heater is listed FVIR, and the heater is protected from vehicles by a barrier, elevation, or location (507.13, 507.13.1).
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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 valves
- 5Water heaters I: tank. Seismic strapping, the T&P discharge line, expansion tanks, sediment traps, pans, venting, and the garage rulesYou are here
- 6Water heaters II: tankless and heat pump. Gas sizing, venting, condensate, the 2025 Energy Code direction, and where the gas-ban ordinances stand
- 7Sewer and drain I: the camera, the locator, hydro-jetting vs. cabling, and when each is the right tool
- 8Sewer and drain II: trenchless vs. open trench, whose lateral it is (it varies by city), backwater valves, and point-of-sale lateral ordinances
- 9Case: the hissing line. The meter test, the supply leak that fed the roots, the lateral to the city tap, and the contract and permit trail
- 10Leak detection: slab leaks, acoustic and pressure methods, thermal imaging, and repipe vs. reroute
- 11Low pressure: the PRV, galvanized pipe, and the sequence that finds which one it is
- 12Sewer gas: trap seals, trap primers, vents, and the sequence that finds the smell
- 13Water treatment: where softeners are restricted in California, filtration, pressure regulators, and thermal expansion
- 14Fixtures and conservation: CALGreen flow rates, SB 407 retrofit-on-alteration and disclosure-on-sale, 1.28 gpf, and the ADA basics a plumber needs
- 15Materials and methods: PEX vs. copper vs. CPVC, ABS vs. PVC (it is regional), cast iron, and the transitions that fail
- 16Commercial basics: grease interceptors, the backflow program, and the tester certification that opens a second line of work
- 17Cal/OSHA for a small shop: the IIPP every employer must have, heat illness prevention, trenching and the 5-foot permit, confined space, silica, and ladders
- 18Environmental rules: EPA lead-safe certification for any pre-1978 home, asbestos and transite pipe, and stormwater
- 19Job-site craft: sequencing with the other trades, protecting the home, and the punch list that ends the job
- 20Case: the water heater that failed inspection twice
- 21Case: the gas leak call. The protocol, and the walk-away
- 22Case: the "customer doesn't want a permit" job
- 23Template: the job-site checklist, from the truck to the walk-through
- 24Template: the pre-inspection checklist by stage. Underground, rough, water heater final, gas, and trim
- 25Template: the Injury and Illness Prevention Program starter for a plumbing shop of one to five
- 26Template: the Heat Illness Prevention Plan for a plumbing shop, outdoor and indoor
- 27Template: the customer options sheet (good / better / best) with the cost band, the permit path, and the code trail on each rung