Water Heater Age Lookup: How Old Is Your Water Heater?

A water heater’s age is hidden in the serial number on its rating plate, but each maker writes the date differently. Bradford White uses two letters for the year and month, and its year letters repeat every 20 years. Rheem puts the month and year in the first four digits: 1209 means December 2009. A. O. Smith has no key on its own site that we could find, so for A. O. Smith, State, American and Whirlpool heaters the honest answer is to ask the maker with your serial number. The lookup above, one of our guides to choosing and sizing a water heater, decodes Bradford White and Rheem from the makers’ own formats and shows every date that fits when the code is ambiguous.

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.

Every result is an estimate. A serial number gives the month the heater was built, not the day it went into your house. Water Heater Handbook sells nothing and recommends no installer or brand.

Find the serial number

The serial number is on the rating plate, the label that also carries the model number and, depending on the heater, the gas type and input rating or the voltage and wattage. A. O. Smith calls it the data plate and, on the atmospheric gas tank its manual covers, puts it next to the gas control valve (A. O. Smith 100263112, January 2015, p. 7). Bradford White’s My Water Heater page shows where its rating plate sits. Rinnai’s N series tankless heaters also come with model and serial number labels printed with a QR code, and the manual’s cover has a space to stick one on (100000467(06), June 2020, cover and p. 18).

• Read, don’t take apart. You don’t need to open a panel, cover or burner door to read a serial number. If the label is hidden or worn, stop there and ask the maker.
• Keep your hands off the vent on a gas heater. A. O. Smith’s manual warns that touching the vent can burn you (100263112, p. 24).
• Leave the labels on. The same manual says not to remove any permanent instructions, labels or the data plate (p. 3).
• Write down the model and serial number together. A. O. Smith asks for both before you call its hotline (p. 1), and a phone photo of the plate saves copying errors: a 0 read as an O changes the answer.

Bradford White: two letters, up to three possible decades

Bradford White’s own pages give the rule. The first character of the serial number is the year letter and the second is the month letter. The rest is a production number: seven digits before December 2007, which Bradford White writes as DM, and eight digits after (Bradford White For The Pro, “Determining The Age Of A Water Heater”, posted 24 May 2020, updated 19 July 2024).

• Month letters: A for January through M for December, skipping I. So A to H are January to August, J is September, K October, L November, M December.
• Year letters: Bradford White skips I, O, Q, R, U and V, which leaves 20 letters, so each letter comes round again every 20 years.
• One exception: Bradford White says a computer error produced some serials starting OA, and those heaters were built in January 1997.

Here is the catch. Bradford White’s two pages print different year tables. The pro page even carries two versions of its own table: the one shown on a wide screen gives A as 2004 or 2024 and B to Z as 1985-2003 or 2005-2023, while the one in its phone layout gives A as 1984 or 2004. The consumer page pairs each letter with 2004-2023 and 2024-2043. Put together, any letter can now mean three years: C can be 1986, 2006 or 2026, and A can be 1984, 2004 or 2024. The table below sets the three runs side by side; we built it from both Bradford White pages, read on 9 November 2026.

Year letter	1984 to 2003 run	2004 to 2023 run	2024 to 2043 run
A	1984 (pro page, phone layout only)	2004	2024
B	1985	2005	2025
C	1986	2006	2026
D	1987	2007	2027
E	1988	2008	2028
F	1989	2009	2029
G	1990	2010	2030
H	1991	2011	2031
J	1992	2012	2032
K	1993	2013	2033
L	1994	2014	2034
M	1995	2015	2035
N	1996	2016	2036
P	1997	2017	2037
S	1998	2018	2038
T	1999	2019	2039
W	2000	2020	2040
X	2001	2021	2041
Y	2002	2022	2042
Z	2003	2023	2043

Three things narrow it down, and the tool uses all three:

1. Count the digits after the two letters. Seven digits point to before December 2007, eight to after it. Bradford White doesn’t say which length December 2007 (DM) itself used, so the tool lets a DM serial fit either count. The count alone separates 2004 from 2024 for an A, or 2006 from 2026 for a C.
2. Rule out the future. In November 2026 a heater can’t date from 2027 or later, so D to Z have only two possible years today.
3. Use what you know for certain. A receipt, a permit or an install date written in the manual can rule out a run. If you only have a guess, leave the range on “not sure” and the tool shows every date that fits.

A check on the rule: Bradford White’s own quick service guide for one generation of its gas controls is headed with the serial date code “TA” and gives it as January 2019 (Quick Service Guide 238-55593-00A). That matches T = 2019 and A = January. More on these labels is in our Bradford White serial number guide.

Rheem: month and year in the first four digits

Rheem’s page says the serial on its water heating rating labels has ten characters (Rheem calls them digits), and gives the example 12 09 D 01234: month made (12), year made (09), a plant line code (D), then a running number (Rheem, “How to locate and read your Rheem water heating serial numbers”, undated, read 9 November 2026). So a serial starting 0517 was built in May 2017.

• The century is our reading, not Rheem’s. Rheem’s page gives only two year digits. The tool reads 00 up to the current year as the 2000s and 80 to 99 as the 1980s and 1990s, and refuses anything in between. Rheem’s page doesn’t say how long this format has been used, so a much older label may not follow it.
• If the serial doesn’t start with four digits, it doesn’t match Rheem’s published format. Don’t force it into the tool; ask Rheem.
• Warranty check: the same Rheem page links to Rheem’s warranty verification tool, which takes the serial number.

Ruud and Richmond. Ruud’s site, which carries a Rheem Manufacturing Company copyright, has its own water heater age calculator that takes the serial number, but the page doesn’t publish the format. Rheem’s serial page names only Rheem. We haven’t read Richmond’s format anywhere. So the tool marks both “not confirmed”: use Ruud’s calculator, or ask the maker.

A. O. Smith, State, American and Whirlpool

This is the brand most people search for, and the one where we have the least to give. On 9 November 2026 we found no page on A. O. Smith’s own site that explains its serial numbers. The other pages we found on the subject are third-party decoder sites, inspector forums and contractor blogs, and they don’t agree with each other on how to read a current serial. We don’t repeat any of them, because a wrong reading can put a heater ten years out.

One federal document shows how some A. O. Smith-built heaters were dated two decades ago. The CPSC’s October 2005 recall notice (recall 06-002) covered certain 75-gallon propane models with the name A.O. Smith, Reliance, Apollo, State or Maytag on the side, made January 2004 to July 2005. It told owners to check the serial on the rating plate, and listed codes such as “MA04 or AA04 or A04” for January 2004 and “G05” for July 2005: a month letter and a two-digit year. That covers those recalled models only. It doesn’t tell you how a 2015 or 2024 A. O. Smith serial reads, so the tool doesn’t use it.

What works: call A. O. Smith with the model and serial number. Its gas water heater manual lists a Technical Assistance Hotline at 1-800-527-1953 (100263112, January 2015). For State, American, Reliance or Whirlpool, use the maker or support number on your own heater’s label or manual. We haven’t confirmed who builds each of those brands today, so we don’t group them under one code.

Rinnai, Navien and other brands

Brand	Maker’s own serial key read?	Where to ask
Bradford White	Yes (updated 19 July 2024)	bradfordwhite.com
Rheem	Yes (undated page)	rheem.com
Ruud	No: calculator only, format not published	Ruud’s age calculator
A. O. Smith	No (2004-05 recall codes only)	Hotline 1-800-527-1953, from its manual
State, American, Reliance, Whirlpool, Richmond	No	The maker named on your label or manual
Rinnai	No	1-800-621-9419 or rinnai.us, from its N series manual
Navien	No	navieninc.com

Rinnai’s tankless manual shows that the unit carries its own record: its limited warranty doesn’t apply to a product whose serial number or manufacture date has been defaced (Rinnai N series Installation and Operation Manual 100000467(06), June 2020, p. 88-89). So Rinnai can date a heater from the label even though it doesn’t publish the key. The same manual says proof of purchase, a dated receipt or registration within 30 days, is needed for warranty service.

When the serial isn’t enough: other clues

• The manual’s front page. A. O. Smith’s gas manual has a box for the date installed, the model and serial numbers and maintenance dates, and tells owners to keep the manual in its pocket on the heater (100263112, p. 1-3). Check for a filled-in copy hanging on the tank.
• A date printed on the label. Read the whole rating plate and any stickers. If one prints a date of manufacture, that is the maker’s own statement and beats any decoding.
• Paperwork. A receipt, an invoice, a home inspection report or the warranty registration usually gives the install date.
• The permit record. Where a permit was pulled for the install, the building department may hold the date. Rules on permits are set locally.

Keep the two dates apart. The serial tells you when the heater was built; it can sit in a warehouse or on a shelf before anyone installs it. For a warranty claim, the maker’s terms in your manual decide which date counts.

What the age tells you, and what it doesn’t

Age is a planning number, not a diagnosis. The federal figures are broad and come with no field data behind them:

Source	What it says	Date
DOE Energy Saver, tankless page	“storage water heaters last 10–15 years”; “Most tankless water heaters have a life expectancy of more than 20 years”	Internet Archive copy, 30 June 2026 (the live page returns 404)
ENERGY STAR, heat pump water heater savings	Uses a 13-year lifespan as an assumption in its savings table	Undated page, read 9 November 2026

DOE’s archived storage water heater page says periodic maintenance can significantly extend a heater’s life, and points readers to the owner’s manual for the schedule (Internet Archive copy, 1 May 2026). Our guide to how long water heaters last sets out what each maker and agency says, side by side. Whatever the age, these don’t wait: a tank leaking from its body, a relief valve that keeps running, a gas smell or a carbon monoxide alarm, and any heater that has been under water. Start with where the water is coming from, and for a gas smell leave the building first and call from outside (what to do about a gas smell or carbon monoxide).

If the heater is old enough that you’re planning a replacement, two dated facts help. From 6 May 2029, a new electric storage heater of 20 to 55 gallons (other than the 20-35 gallon “small electric” class) must reach a uniform energy factor (UEF, the federal efficiency rating) of 2.30, and one over 55 to 120 gallons 2.50 (10 CFR 430.32(d)(2), Table 14, read 9 November 2026). That applies to heaters made from that date; it doesn’t touch the one in your basement and isn’t a ban. And size the next one from your household’s busiest hour with our first hour rating calculator (first hour rating: how much hot water a tank can deliver in an hour of use) rather than copying the old tank’s gallons.

Once you know the brand and model, also look it up in the CPSC’s recall list. The 2005 A. O. Smith notice above is one example of a recall that names serial ranges.

Worked example

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.

A Bradford White rating plate reads (an invented example) TA12345678, checked in November 2026.

1. T is the year letter: 1999, 2019 or 2039 by the table. 2039 is in the future, so it’s out.
2. A is the month letter: January.
3. Eight digits follow the letters, so the heater was built in December 2007 or later. 1999 is out.
4. One date fits: January 2019. From January 2019 to November 2026 is 94 months, which the tool shows as 7.8 years, an estimate.

Now say the plate is worn and you can’t count the digits. Set “how many digits” to “not sure” and the tool shows two dates: January 2019 (7.8 years) and January 1999 (27.8 years). That’s where the clues above settle it: an invoice for a new heater installed in spring 2019 points to the 2019 date; a filled-in manual from 1999 points the other way.

A Rheem plate starting 1209 (Rheem’s own example) reads December 2009: 203 months to November 2026, or 16.9 years.

Your next step

• Now: photograph the rating plate, without opening any panel, and note the brand, model and serial number.
• Bradford White or Rheem: enter the characters in the lookup above. If more than one date fits, check the digits and your paperwork.
• Any other brand: call or write to the maker with the model and serial number, using the contact on your label or manual or the table above.
• Planning ahead: compare what each fuel would cost to run with our yearly energy cost tool, and get written quotes from licensed installers; prices vary.
• Can’t wait: a gas smell (leave, then call 911 or the gas utility from outside), a carbon monoxide alarm (get everyone into fresh air, then call 911), a relief valve that keeps discharging, or a tank leaking from its body.

Sources checked on 9 November 2026. Fact-check note: serial formats come only from the makers’ own pages (Bradford White, Rheem) and, for 2004-05, a CPSC recall notice. Where we found no maker key, we say so and give no date.