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How old is my A.O. Smith and State water heater?
On A.O. Smith and State water heaters made since about 2008, the first four digits of the serial number are the date: the first two are the year and the next two the week. 1324… is 2013, week 24, which is June. Older ones use the codes below.
Reading the code
11324A001234: Since about 2008: year, then week. 2013, week 24 (June).
2AF04A093001: Older: two letters, then the year. 2004; the second letter, F, is the month (June).
3E07A135491: Older: a letter for the month, then the year. May 2007.
40399 1234567: Older: month, then year. March 1999.
State Water Heaters is part of A.O. Smith and uses the same codes.
Which week is which month
| January weeks 1–5 | February weeks 6–9 | March weeks 10–13 |
| April weeks 14–18 | May weeks 19–22 | June weeks 23–26 |
| July weeks 27–31 | August weeks 32–35 | September weeks 36–39 |
| October weeks 40–44 | November weeks 45–48 | December weeks 49–53 |
Where the serial number is
On the rating label on the side of the tank, usually near the top, marked "Serial No." or "S/N".
How long they last
Most tank heaters last 8 to 12 years. Warning signs: rusty hot water, rumbling, water at the base. What a replacement costs, and the permit.
Other makers
Bradford White · Rheem and Ruud · Any brand, from a photo