American water heater age by serial number
The serial number is on the data plate on the front of the heater. On an American water heater the first two digits of the serial are the year and the next two are the week.
Decode an American serial number
How to read an American serial number
Year and week, first four digits
The first two digits are the year and the next two are the week of that year.
Shape: ten digits, or four digits, a letter and six digits. Newer serials can be thirteen digits.
9950123040 reads as week 50 of 1999 (around December).
Where to find the serial number
The data plate is on the front of the tank jacket.
If the serial number does not decode
- The small print at the bottom of the plate names the company that built the heater. Store brands changed makers over the years.
- The American Water Heater Company also builds or built U.S. Craftmaster, American ProLine, Envirotemp, Mor-Flo, Premier Plus and Powerflex heaters. They read the same way.
- Older American Appliance and Mor-Flo serials are plain sequence numbers. They carry no date.
- The manufacturer can confirm the date from the serial: American registration, warranty or serial lookup.
What the age tells you
| Equipment | Typical service life |
|---|---|
| Tank water heater | 10 to 15 years |
| Tankless water heater | about 20 years |
About American
The American Water Heater Company of Johnson City, Tennessee builds American, Whirlpool-brand and U.S. Craftmaster water heaters and many store brands. A. O. Smith has owned it since 2006. American used the year-and-week serial long before A. O. Smith adopted the same order for its own brands.
Brands that share this serial system: Whirlpool, A. O. Smith, State, Reliance.
Questions and answers
Which characters in an American serial number show the date?
The first two digits are the year and the next two are the week of that year. This applies to units built since at least the late 1990s.
Sources
- CPSC recall: American Water Heater Company gas water heaters, serials starting 0124 to 0127 sold June to September 2001 (US Consumer Product Safety Commission): https://www.cpsc.gov/Recalls/2001/cpsc-american-water-heater-co-announce-recall-to-replace-burners-in-gas-water-heaters
- CPSC recall 19-029: A. O. Smith ultra-low NOx water heaters, serial ranges by build date (US Consumer Product Safety Commission): https://www.cpsc.gov/Recalls/2019/A-O-Smith-Recalls-Ultra-Low-NOx-Water-Heaters-Due-to-Fire-Hazard
- Building Intelligence Center: American water heater age (independent reference): https://www.building-center.org/american-water-heater-age/
- InspectAPedia: American water heater age (independent reference): https://inspectapedia.com/plumbing/American-Water-Heater-Age-Manuals.php
Formats last checked against these sources on October 5, 2026. Found a serial that does not fit? Send a correction. How formats are verified: method and sources.