Water Heater Handbook

How We Check

Where Water Heater Handbook's steps and figures come from: makers' manuals by part number, federal rules and model codes by section, and disagreements shown.

Water heater advice is easy to get wrong. Heaters differ by maker, model and year, the makers disagree with each other and sometimes with the federal agencies, and old figures keep circulating after they change. The Department of Energy’s own Energy Saver pages on water heaters have been offline since about July 2026; they now survive only as archived copies. The federal tax credit for water heaters ended for property placed in service after 31 December 2025 (IRS, read 9 November 2026), yet pages still promise it. A wrong step can cause a gas leak, carbon monoxide poisoning, a shock, a scald or a relief valve hazard. This page sets out where our steps and figures come from, why steps follow the maker, how we show sources that disagree, how often everything is rechecked, which documents we use, and where our limits are.

General information, not professional advice. Gas, 240-volt power, scalding water and a pressurised tank can hurt you. Follow the label and manual on your own heater; where they say to stop and call a qualified technician, stop. Codes and licensing rules are set locally.

Where steps and figures come from

We go to the source that wrote the step or the rule, and link it at the claim:

  • Makers’ manuals, by part number and print date. Owner’s guides, installation and operation manuals, service manuals, lighting labels and technical bulletins, found from the maker’s own product page or document library and read in full around the step we use. Every step names the document, its part number, its date and, where it helps, its page. The manuals are copyrighted, so we describe them in our own words and quote only a short caution or stop line.
  • Federal rules in the eCFR: the efficiency standards for water heaters in 10 CFR 430.32, the test procedure behind the ratings in Appendix E to Subpart B of Part 430, and the FTC’s EnergyGuide label rules in 16 CFR part 305, each with the date the eCFR text was current.
  • Federal safety agencies: the Consumer Product Safety Commission on scalds and carbon monoxide alarms, the CDC on carbon monoxide and on Legionella, the EPA on indoor carbon monoxide, and the Pipeline and Hazardous Materials Safety Administration (PHMSA) on what to do about a gas smell.
  • The Department of Energy, including its archived pages. DOE’s Energy Saver pages on sizing, storage, tankless and heat pump water heaters now return “page not found”. We cite the Internet Archive’s copies with their capture dates, label them as archived, and replace them with the live text if DOE puts the pages back.
  • ENERGY STAR: its criteria for water heaters (Version 5.0, effective 18 April 2023, as of 9 November 2026), and its own guidance and savings figures, quoted with the assumptions printed beside them.
  • The Energy Information Administration: annual average residential electricity and natural gas prices, by state and year, with the release date, and its Btu conversion factors.
  • The IRS and Congress: the IRS’s pages and the tax code for credits, and public laws as enacted, such as Public Law 119-6.
  • Model codes, by section and edition: the International Residential Code (2024 edition) for drain pans, garage installation, seismic bracing, relief valves and thermal expansion, cited as the model code that states and cities adopt and amend, never as the law where you live. Codes are copyrighted, so we paraphrase them.
  • State law in official text, where a page needs it, such as California’s water heater strapping rule (Health and Safety Code 19211) or Massachusetts’s permit rule for gas fitting (248 CMR 3.05).
  • Never a source: plumber, heating and contractor pages, retailers’ advice pages, home-improvement magazines, “best water heater” and comparison sites, serial number decoder and inspector sites, forums and videos. They can point us to a maker’s document, but they never carry a step or a figure on a page.

Why steps follow the maker, and stop where the maker stops

A maker’s manual describes its own heater: its controls, its venting, its parts and the order of the steps. It also says where an owner should stop and who should do the rest. So a step reaches our pages only if a maker’s own document gives it for that kind of heater, and the maker’s stop line goes in at the step it belongs to. If no maker document we have read gives steps for a job, the page explains the part and gives no steps.

The makers don’t draw that line in the same place, and we show where each one draws it. Replacing the gas control valve on a gas heater is one example. A. O. Smith’s owner’s guide for its atmospheric gas heaters (100263112, January 2015) gives the steps, while its cover says installation and service must be performed by a qualified installer, service agency or the gas supplier. Rheem’s use and care manual (AP23698) and Bradford White’s installation and operation manual (238-51012-00V, REV 08/26) tell owners not to attempt repair of the gas control, burners or gas piping, and to refer repairs to a qualified technician. All three were read on 9 November 2026, and a page on that job quotes all three. Electric heaters are similar: A. O. Smith’s electric guide (100309797 Rev B, September 2020) gives owners element and thermostat replacement, opening with a line that says to have a qualified person do the work if you are not comfortable doing it, while Rheem’s and Bradford White’s electric manuals tell owners not to attempt repair of elements, thermostats or wiring. Pages name whose manual each step comes from and never say “the manual” as if there were one.

Every step page also says to follow the label on your own heater. Lighting steps for a standing pilot, a piezo igniter and an electronic control are not the same, and a step written for one can be wrong on another.

How a fact gets on the page

Each step and figure is sorted by how directly it was read, and that decides how we word it:

  • Read in the primary text: the maker’s document, the federal rule, the agency’s page or the code section. We state it plainly, with the citation and the date we read it. Before a writer uses it, the whole chapter or section is read again, not just the line that matched a search, because cautions and exceptions often sit further down.
  • Read only in part, in an archived copy, or in an undated maker web page. It is labelled for what it is, such as “DOE’s archived page, captured 1 May 2026”, and never stated as more than that.
  • Not read. It stays off the page, or the page says “not confirmed” and links the maker’s or agency’s own page. “Not confirmed” says nothing about what the answer is.

How we show sources that disagree

Where makers or agencies give different answers, the page shows each one, with its document and date, side by side. We never average them and never quietly pick one. Flushing and anode checks are the clearest cases:

SourceDraining or flushing a storage tankChecking the anode rod
A. O. Smith gas guide 100263112 (January 2015)After the first six months, then about once a year if there is little sediment, more often if there is a lotAfter the first six months, then at least yearly; more often with a water softener
Rheem use and care manuals (gas AP23698, electric AP17547-1)A few quarts every monthRemoved and inspected yearly
Bradford White manuals 238-51012 and 238-44422 (REV 08/26)Gas manual: a gallon a month, listed among the jobs for a qualified service technician. Electric manual: drain monthly until the water runs clearAbout every two years, more often with softened water
DOE Energy Saver, archived 1 May 2026A quart every three monthsEvery three to four years
Each maker’s figure is for its own heaters. All read 9 November 2026. Follow the manual for your model.

The same goes for the space a heat pump water heater needs. ENERGY STAR’s guidance is an interior space that stays between 40°F and 90°F year-round, with 1,000 cubic feet of air space around the heater (ENERGY STAR, read 9 November 2026), while individual makers’ manuals give their own room sizes and temperature ranges for their own models. Pages give ENERGY STAR’s figure as guidance and tell you to check your model’s installation manual.

How figures are dated

  • Standards with their start dates. From 6 May 2029, electric storage water heaters of 20 to 55 gallons, other than the small electric class of 20 to 35 gallons, must reach a uniform energy factor of 2.30, and those over 55 and up to 120 gallons 2.50 (10 CFR 430.32(d), read 9 November 2026). Pages give the rule in force today and the date the next one applies.
  • Prices with their year and release. Energy costs use the EIA’s annual average residential prices for 2025, with the release date, by state where the EIA gives one; you can enter your own price from your bill instead.
  • Criteria by version. ENERGY STAR figures name the criteria version they come from.
  • Archived pages by capture date. Every DOE Energy Saver figure carries the date the archived copy was captured.
  • A read date on everything. In text, tables and graphics, each figure carries its source and the day we read it, and each page ends with the date its sources were checked.

How calculators work

Our calculators do arithmetic on numbers you enter, using a method they name, and show each step and say “estimate” on every result. The tank size calculator follows DOE’s peak-hour method from its archived sizing page, with DOE’s own per-use gallons as editable defaults. The tankless size calculator adds up the flow of fixtures used at once and works out the temperature rise from an inlet temperature you enter. The age lookup reads only the serial number formats we have confirmed from the makers themselves, and where a format repeats, it shows every date a serial could mean. The expansion tank tool uses an expansion tank maker’s published sizing method. The heat pump fit check compares your room with ENERGY STAR’s guidance. The yearly energy cost tool uses EIA prices and the efficiency ratings in the federal standards and ENERGY STAR’s criteria, labelled as which.

Each formula is tested against answers worked by hand before the calculator goes live. Every default says where it comes from and when we read it, or that it is our assumption, and you can change it. No calculator says what heater to buy, that a heater will meet your needs, or how old your heater is for certain.

How pages are checked

After a page is written, a separate fact-check compares each step, caution, stop point, temperature, pressure, interval, size, rating, date and code section with its source, and reworks every sum on the page. A final review looks for errors, gaps and anything that could lead a reader into a gas, electrical, scald or pressure hazard. A page with a serious problem still open does not go out.

How often figures are rechecked

  • Energy prices: each quarter, and when the EIA publishes a new year’s annual averages.
  • ENERGY STAR criteria and guidance: each quarter.
  • Federal efficiency standards and label rules: each year, and whenever DOE, the FTC or Congress changes a rule.
  • Makers’ manuals, labels, serial number formats and error code lists: each year, and when we learn of a new revision.
  • Model codes: when a new edition is published.
  • Rules with a known start date, such as the 6 May 2029 standards: when the date arrives.
  • Safety guidance from CPSC, CDC, EPA and PHMSA, tax credits and everything else: at least every six months, and sooner when we learn a source has changed.

A page shows an updated date only when its content really changed. Between rechecks a maker can revise a manual without our knowing, which is why every step names the document and date it comes from.

What is an assumption

Where we work something out ourselves, we say so. Arithmetic is shown step by step, and a figure worked from a federal formula, such as the minimum rating for one tank size, is labelled as our arithmetic. A conclusion a source does not state is labelled as ours. Lifespans and savings are given only as the named source’s figure, with its assumptions: DOE’s archived page says storage water heaters last 10 to 15 years, and ENERGY STAR’s savings table assumes a 13-year life for a heat pump water heater. Neither is a measurement of heaters in homes.

How we treat claims seen elsewhere

Claims from sellers are reported as claims, never as fact, and we don’t name a seller when we question one. Some lines you may see, checked on 9 November 2026:

  • “The federal tax credit pays up to $2,000 for a heat pump water heater.” Not any more. The energy efficient home improvement credit does not apply to property placed in service after 31 December 2025 (IRS). See water heater rebates.
  • “Electric water heaters are banned from 2029.” Not as stated. From 6 May 2029, most electric storage heaters over 20 gallons must reach heat-pump-level ratings, but a small electric class of 20 to 35 gallons keeps its own standard (10 CFR 430.32(d)).
  • “Gas tankless water heaters are being banned.” No. Congress disapproved DOE’s December 2024 standards for gas-fired instantaneous water heaters, and they have no force or effect (Public Law 119-6, approved 9 May 2025).
  • “A dripping relief valve means the valve is bad.” Often not. A. O. Smith’s guide says a drip usually means the water pressure is too high or there is no expansion tank, and to have a qualified person replace the valve only if it still drips once those are dealt with. Never plug or cap it. See relief valve dripping or leaking.
  • “Heat pump water heaters don’t have an EnergyGuide label.” DOE’s archived sizing page said so, but the FTC’s current rule counts heat pump units in its definition of a water heater (16 CFR 305.2). We follow the rule, not the archived page.
  • DOE’s own sizing example. DOE’s archived worksheet adds 60, 2 and 3 gallons and prints 66. The sum is 65. Our tank size calculator uses DOE’s method with the correct arithmetic, and says so.

The sources we use

These are the main documents behind our pages, as of 9 November 2026. Each page names the ones it relies on, at the claim.

Makers’ documents

Federal rules and agencies

DOE Energy Saver pages (archived)

Model codes and state law

  • International Residential Code, 2024 edition: Chapter 28, water heaters (P2801 to P2804), P2903.3 and P2903.4 (water pressure and thermal expansion), M2005 (fuel-fired heaters in bedrooms, bathrooms and closets) and R301.2.2.10 (seismic bracing), read on the ICC’s free public viewer
  • California Health and Safety Code 19211 (water heater bracing)
  • Massachusetts 248 CMR 3.00 (plumbing and gas fitting permits)

Our limits

Some sources can’t be read in full, because they are behind an account or a paywall, or have not been published. As of 9 November 2026 we have not read the National Fuel Gas Code (NFPA 54), the Uniform Plumbing Code or ASHRAE Standard 188, so no page quotes them. We have not found a maker’s own serial number guide for the A. O. Smith group’s current heaters, Rinnai or Navien, so our age lookup leaves those brands out and links the maker. We have read Rinnai’s error codes only for its N series, so pages say which series they cover, and we have not read Navien’s or Rheem’s tankless code lists. We have not read every state’s or city’s rules on who may do gas work, so pages say to ask your building department. Rebate amounts appear only with a dated program source. No check catches everything, so please tell us if you find a mistake. Fixes are logged on our corrections page, and our editorial policy covers the rest of how pages are made.

Before you rely on a step here, check it against the label and manual on your own heater. If you smell gas, a carbon monoxide alarm sounds or a relief valve won’t stop discharging, don’t wait for a recheck of ours: leave, or shut off the heater as the label says, and call for help.

Sources on this page checked on 9 November 2026.