A. O. Smith date code: year, then month or week
A. O. Smith says to read “the first four numbers, ignoring any letter that may start the serial number.” The first two numbers are the year. The next two are the month for heaters built before 2008, and the week for heaters built after 2008.
What is A. O. Smith's rule?
| Part of the serial | Built before 2008 | Built after 2008 |
|---|---|---|
| Leading letter, if any | Ignore | Ignore |
| Digits 1–2 | Year | Year |
| Digits 3–4 | Month | Week |
A. O. Smith's international site gives the same year-and-week layout. Its example serial starts with 20 and 37, which it reads as week 37 of 2020, “between September 7 and 13, 2020.”
What does my serial say?
What about heaters built in 2008?
A. O. Smith's FAQ says “before 2008” and “after 2008” but does not say which rule applies to units built in 2008. For a code starting 08, our reader shows both the month and the week reading.
Which A. O. Smith sites is this from?
Both rules come from A. O. Smith sites: hotwatercanada.ca is A. O. Smith's Canadian site, and aosmithinternational.com is its international site. Neither is A. O. Smith's US site. If your heater carries a different serial format, these rules may not apply.
Sources
- A. O. Smith Canada, FAQs: https://www.hotwatercanada.ca/faqs/, accessed 2026-10-27
- A. O. Smith International, Production date of my device: https://aosmithinternational.com/manufacturing-date-device/, accessed 2026-10-27