Pick the brand, type the serial number from the label, and get the month it was built, how old it is, and whether it's worth repairing.
Check the label first
Some labels print the date outright. Rheem, Ruud, and Richmond labels made since 2012 show a manufacture date (“MFG. DATE”), and American Water Heater labels can show a “BUILD DATE.” If yours has one, that's your answer. If not, the serial number carries a date code, and each manufacturer writes it differently.
Bradford White
The first two letters of the serial number are the year and the month. The month letters run A for January through M for December, skipping I. Each year letter repeats every 20 years, so the length of the number after the letters tells them apart: seven digits before December 2007, eight digits after. Example: JC16433183 was built in March 2012.
| First letter | Year |
|---|---|
| A | 2004 or 2024 |
| B | 2005 or 2025 |
| C | 2006 or 2026 |
| D | 2007 or 2027 |
| E | 2008 or 2028 |
| F | 2009 or 2029 |
| G | 2010 or 2030 |
| H | 2011 or 2031 |
| J | 2012 or 2032 |
| K | 2013 or 2033 |
| L | 2014 or 2034 |
| M | 2015 or 2035 |
| N | 2016 or 2036 |
| P | 2017 or 2037 |
| S | 2018 or 2038 |
| T | 2019 or 2039 |
| W | 2020 or 2040 |
| X | 2021 or 2041 |
| Y | 2022 or 2042 |
| Z | 2023 or 2043 |
Rheem, Ruud, and Richmond
Older serial numbers start with four digits: the month, then the year (0912D01234 is September 2012). Since April 2012, they start with a plant letter (A, W, Q, M, or C), then the week and the year: Q231299996 was built in week 23 of 2012, and its label reads May 30, 2012. Some labels print extra letters in front of that, which the decoder skips.
A.O. Smith, State, American, Reliance, U.S. Craftmaster, and Whirlpool
The first four digits are the year and the week: 1544102180400 was built in week 44 of 2015, and its label reads October 28, 2015. A.O. Smith confirms this for heaters made since 2011, including Kenmore units it built.
Tankless brands
Bosch puts a three-character month code right after the first four characters of the serial (for example 720 is April 2017), and the decoder has its full chart through 2030. Older Navien NR and NP units carry the product date in the label code as year, month, and day. We couldn't find a published date code for Rinnai, Noritz, Takagi, or newer Navien units, so for those, text us a photo of the label and we'll read it.
How old is too old?
A tank water heater typically lasts about 8 to 12 years, and Front Range hard water pushes it toward the short end. Under about eight years old, a failed part is usually worth repairing; at ten or older, or with any leak from the tank itself, replacement is the better money. Tankless units typically last 15 to 20 years with yearly descaling. How long water heaters last in Colorado · Water heater leaking? · Water heater repair and replacement
Sources (each manufacturer's own pages and documents): Bradford White: determine the age of my water heater · Bradford White: serial number date code chart · Rheem: how to read Rheem water heating serial numbers · Rheem Technical Service Bulletin 1207 (serial numbers, including the April 2012 format) · A.O. Smith recall release (brands and the year-week serial rule) · Bosch serial number reference guide · Navien NR/NP service manual: locating the serial number. Checked October 27, 2026.