A. O. Smith date code: year, then month or week

Last updated: 2026-10-28

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.

A. O. Smith's rule

A. O. Smith serial date 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

Source: A. O. Smith Canada (hotwatercanada.ca), FAQs, “How to read a A. O. Smith serial number”. A. O. Smith's example: serial U0106413635 “was manufactured in June 2001”.

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.”

Source: A. O. Smith International, Production date of my device.

What your serial says

Serial number from the rating label

Type the serial to see the possible dates.

The reader uses only the maker's rule shown on this page. Two-digit years read as 20xx, or 19xx when 20xx would be in the future. It runs in your browser and sends nothing anywhere.

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.

The A. O. Smith sites these rules come 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

Other makers: Rheem, Bradford White, Goodman and Amana. All date codes.