Water Heater Age Chart: Every Serial Number Format by Brand

Water Heater Age Chart by Serial Number

Every major water heater brand hides its manufacture date in the serial number on the rating plate — but each brand hides it differently. This chart lines up every format this site decodes, so you can identify the pattern at a glance, then jump to the free decoder for that brand. The formats below come straight from our decoder code, so the chart stays honest as the decoders are maintained.

Brand	Manufacturer	Serial format	Example	Decoder
Rheem	Rheem Manufacturing	Letter prefix, then MMYY (month + year); older units use WWYY (week + year); tankless often MM.YY-xxxxx	R 0819 B10488 → August 2019	Rheem lookup
Ruud	Rheem Manufacturing	Same as Rheem — shared factories and date codes	RU 0904B21710 → September 2004	Ruud lookup
Richmond	Rheem Manufacturing	Same as Rheem	A141511869 → week 14 of 2015	Richmond lookup
A.O. Smith	A.O. Smith	YYWW in the first four digits (year + week); pre-2008 units may open with a month letter	1914B000123 → week 14 of 2019	A.O. Smith lookup
State	A.O. Smith	Same as A.O. Smith since the 2001 acquisition	1604J004619 → week 4 of 2016	State lookup
Reliance	A.O. Smith	Same as A.O. Smith	1811A002456 → week 11 of 2018	Reliance lookup
Kenmore	Rebadged — mostly A.O. Smith, some Rheem or Whirlpool	Varies by supplier; most are A.O. Smith-style with the year in the 2nd and 3rd digits	A03307353 → 2003 (A.O. Smith style)	Kenmore lookup
Bradford White	Bradford White	Two letters: 1st = year (20-year cycle), 2nd = month (A–M, skip I)	FG1234567 → July 1989 or July 2009	Bradford White lookup

Bradford White Year-Letter Chart

Bradford White is the outlier in the table above, so it earns its own chart. The first letter of the serial is the year on a 20-year repeating cycle (skipping I, O, Q, R, U, and V), and the second letter is the month, A through M skipping I — so A = January … M = December.

Letter	Years	Letter	Years
A	1984 / 2004 / 2024	L	1994 / 2014
B	1985 / 2005 / 2025	M	1995 / 2015
C	1986 / 2006 / 2026	N	1996 / 2016
D	1987 / 2007	P	1997 / 2017
E	1988 / 2008	S	1998 / 2018
F	1989 / 2009	T	1999 / 2019
G	1990 / 2010	W	2000 / 2020
H	1991 / 2011	X	2001 / 2021
J	1992 / 2012	Y	2002 / 2022
K	1993 / 2013	Z	2003 / 2023

Because the cycle repeats, F can mean 1989 or 2009 (and the cycle keeps extending in both directions). To pick the right year, weigh the unit's condition, the ANSI standard revision year printed on the rating plate, and the age of the house — a water heater can't be older than the building it serves. Our Bradford White decoder lists every plausible year rather than guessing.

How to Use This Chart

1. Find the rating plate. It's a silver or white sticker on the side of the tank, usually in the upper half. On tankless units, check the side panel or behind the front cover.
2. Check for a printed date first. Many newer Rheem-built plates show "MFG. DATE" in plain text — that always beats decoding.
3. Match the serial to a row above. If the first four characters are digits, think A.O. Smith family (year + week) or Rheem family (month + year). Two leading letters means Bradford White.
4. Open the brand's decoder. It validates the format, flags impossible characters, and handles the ambiguous cases — like Bradford White's repeating years or A.O. Smith's two-digit years.

One caution that applies to every brand: a two-digit year can point to more than one decade. 0414... on an A.O. Smith-built unit could be 2004 or 2014. When the difference matters — warranty claims, home sales — corroborate with the model number and the unit's apparent condition.

Why the Age Matters

Tank water heaters average 8–12 years of service. Past that window, internal corrosion makes tank failure — and a flooded floor — much more likely. Knowing the exact manufacture date tells you whether a warranty claim is still possible (most tank warranties run 6–12 years from the manufacture date, not the install date), and lets you schedule a replacement calmly instead of paying emergency rates after a leak.

Sources

Serial formats on this page are compiled from our own decoder implementations, each verified against manufacturer and industry references: the InterNACHI water heater dating chart, Bradford White's official serial-number guidance, Rheem's guide to reading serial numbers, A.O. Smith's production-date guidance, and the Building Intelligence Center water heater age guides.