In the Field · Part 4
Water heaters II: tankless and heat pump. Gas sizing, venting, condensate, the 2025 Energy Code direction, and where the gas-ban ordinances stand
The two water heaters that are not a tank each turn a four-hour swap into a design job. A gas tankless unit draws four to six times the input of the tank it replaces, so the gas line, the venting, and the condensate drain are the job, not the heater. A heat pump water heater draws almost no gas and instead needs a 240-volt circuit, air, a place for the condensate, and a customer who understands recovery time. Both are where California's energy policy is pointed: the 2025 Energy Code makes heat pump water heating the prescriptive baseline for new homes and additions. And both are the subject of local politics: the Berkeley gas ban was struck down in federal court in 2023 and repealed, and the South Coast air district's proposed zero-NOx water heater rule was voted down in June 2025. This lesson gives the method for each unit and the current state of the rules so the sale is honest.
What the full lesson covers
- Tankless gas: size the gas line for the unit's full input on the longest run of the whole system (CPC 1215.1.1); most 1/2-inch branches that fed a 40,000 BTU tank cannot feed a 150,000 to 199,000 BTU tankless, and a new 3/4-inch or 1-inch run from the meter is normal.
- Tankless venting is Category III or IV per the listing, with the listed vent material, terminations, and clearances; condensing units produce acidic condensate that goes to an approved drain (CPC 814.1), through a neutralizer where the AHJ or the manufacturer requires it.
- Heat pump: a 240-volt dedicated circuit by an electrician, the manufacturer's minimum air volume or ducting, a condensate drain, and a location where the cool exhaust air and the compressor noise are acceptable.
- Policy: the 2025 Energy Code (effective January 1, 2026) makes heat pump water heating the prescriptive baseline for new single-family construction and additions; replacing an existing gas heater with gas in an existing home remains lawful under state law and the compliance forms for alterations govern.
- Gas bans: Berkeley's ordinance was held preempted by federal law (9th Cir. 2023) and repealed; cities have moved to other approaches; the SCAQMD zero-NOx water heater amendment failed on June 6, 2025. Check the city and the air district before telling a customer what they may or may not install.
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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 rules
- 6Water heaters II: tankless and heat pump. Gas sizing, venting, condensate, the 2025 Energy Code direction, and where the gas-ban ordinances standYou are here
- 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