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A.O. Smith / State water heaters

How old is my A.O. Smith water heater?

Enter the serial number from the label. The date comes from A.O. Smith's documented serial rules, not a guess.

Look for “Serial No.” or “S/N” on the label. Spaces and dashes are fine.

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How to read a A.O. Smith water heater serial number

A.O. Smith and State water heaters encode the manufacture date at the start of the serial number. Since about 2008 the first four digits are the year and week. Older units use a month letter followed by a two-digit year.

  • Year + week (2008 onward)

    Example: 1210A002243 (A.O. Smith) was made in March 2012. For heaters built since about 2008, the first four digits are the year and week of production: "12" is 2012 and "10" is week 10.

  • Factory letter + month letter + 2-digit year (about 1991–2007)

    Example: AF04A093001 (A.O. Smith) was made in June 2004. On older A.O. Smith and State heaters the first letter is the factory code, the second letter is the month ("F" = June) and the next two digits are the year (2004).

Not decoded yet: Pre-2008 all-numeric serials (A.O. Smith Canada), 1970s formats and tankless models are not decoded yet.

Where to find the serial number

The rating label is on the side of the tank: near the gas control valve on gas models, or above the upper heating-element cover on electric models.

The rating label is on the side of the tank, above the gas valve or the upper element cover.

The serial number is usually the longer code on the label, near the barcode. A leading letter such as “S” can be ignored on newer units.

A.O. Smith water heater model numbers

If the brand name isn't visible on the label, the model number can help. Model numbers like these follow A.O. Smith's published nomenclature:

How long does a water heater last?

A typical water heater lasts about 8–12 years. That's a general estimate: maintenance, usage, climate and installation all matter, and age alone doesn't tell you a unit's condition.

Range from A. O. Smith: when to repair or replace a water heater and Lennox: when to replace a water heater.

A.O. Smith water heater recalls

From the U.S. Consumer Product Safety Commission, checked 2026-09-29. A decoded result checks your model number against recalls live.

Questions

How can I tell how old my A.O. Smith water heater is?
Find the serial number on the rating plate and enter it above. A.O. Smith water heaters use the A.O. Smith / State water heaters serial format, which includes the manufacture date. For example, 1210A002243 was made in March 2012: For heaters built since about 2008, the first four digits are the year and week of production: "12" is 2012 and "10" is week 10.
Where is the serial number on a A.O. Smith water heater?
The rating label is on the side of the tank: near the gas control valve on gas models, or above the upper heating-element cover on electric models.
How long does a water heater usually last?
A typical service life is about 8–12 years. That's a general estimate: maintenance, usage, climate and installation all matter, and age alone doesn't tell you a unit's condition.
Do State water heaters use the same serial format?
Yes. A.O. Smith and State use the same serial-number conventions (A.O. Smith / State water heaters), so the same decoding rules apply.
How reliable is the result?
The A.O. Smith / State water heaters rules come from documented sources, but they're in Beta while we check more real-world examples, so results are capped at medium confidence. If a serial doesn't match a documented format, we say so instead of guessing.
What does 1210A002243 mean?
The first two digits are the year (2012) and the next two are the week (week 10, early March).
Does this work for State water heaters?
Yes. State is part of A.O. Smith and uses the same serial-number conventions.
Why isn't my older all-numeric serial decoded?
Some pre-2008 units (notably from A.O. Smith Canada) used year + month in the same position newer units use year + week. We can't tell them apart reliably yet, so we don't guess.

Same serial format: State water heater

Sources

Rules last reviewed 2026-09-28. These rules are in Beta while we verify more real-world examples, so results are capped at medium confidence.

Manufacture dates are decoded from manufacturer serial-number conventions and available documentation. Serial formats can change. Verify critical equipment information with the manufacturer when necessary.