How to Find Your Water Heater's Age From the Serial Number
By Andrew Norman · Updated May 2026
Water heaters are one of the most overlooked systems in a home — until they fail. Most residential gas and electric water heaters last 8–12 years before the tank starts to corrode or the elements and thermostats begin failing. Knowing your unit's age is the first step toward knowing when to start budgeting for a replacement.
Instant result:
Use our free decoder — paste the serial number, select your brand, and get the manufacture date immediately.
Where to Find the Serial Number on a Water Heater
The data plate is on the side of the tank, typically in the upper third. It includes the brand name, model number, serial number, BTU or wattage, capacity, and energy efficiency ratings. If the label is damaged, check for a secondary sticker near the pressure relief valve.
Rheem / Ruud Water Heaters
Rheem and Ruud are the same company and are the most common water heater brand in the US.
First character = Month (A=Jan, B=Feb, C=Mar, D=Apr, E=May, F=Jun, G=Jul, H=Aug, J=Sep, K=Oct, L=Nov, M=Dec)
Second character = Last digit of the year
Example: F9XXXXXXX = June 2009 or June 2019
AO Smith Water Heaters
AO Smith also manufactures under the American and State brands for Home Depot and Lowe's respectively.
Current format: YYMXXXXXXX
YY = Year (e.g., 18 = 2018), M = Month (A=Jan through M=Dec, skipping I)
Example: 18CXXXXXXX = March 2018
Bradford White Water Heaters
Bradford White uses an alpha-year code where a letter represents the year (cycling every 20 years). The first character is the year code, the second is the month.
| Letter | Year | Letter | Year |
|---|---|---|---|
| A | 1984 / 2004 | L | 1995 / 2015 |
| B | 1985 / 2005 | M | 1996 / 2016 |
| C | 1986 / 2006 | N | 1997 / 2017 |
| D | 1987 / 2007 | P | 1998 / 2018 |
| E | 1988 / 2008 | R | 1999 / 2019 |
| F | 1989 / 2009 | S | 2000 / 2020 |
| G | 1990 / 2010 | T | 2001 / 2021 |
| H | 1991 / 2011 | U | 2002 / 2022 |
| J | 1992 / 2012 | V | 2003 / 2023 |
| K | 1993 / 2013 | W | 2004 / 2024 |
How Long Should a Water Heater Last?
Standard tank-style gas water heaters typically last 8–12 years. Electric models can go 10–15 years. Tankless water heaters can last 20+ years with regular maintenance.
Key signs that a water heater is near end of life:
- Rust-colored water — interior tank corrosion. Time to replace.
- Rumbling or popping sounds — sediment buildup, often indicates end of life on older tanks.
- Visible corrosion or moisture around the base — replace before it becomes a flood.
- Insufficient hot water — on an older tank, usually a failing element or burner.
Repair vs. Replace Decision
- Under 6 years old: repair most things
- 6–10 years old: repair elements and thermostats; consider replacing on major issues
- Over 10 years old: replace rather than repair anything significant
Find out your water heater's age with our serial number decoder.