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How old is my A.O. Smith water heater?
Type the serial number from the A.O. Smith label to see when it was built.
Example
- 17Year: 17 = 2017
- 19Week: 19 (around May)
Built Week 19 of 2017 (around May)
9 years, 5 months old
In replacement window. Inside the usual 6 to 12 year lifespan, so replacement could come any time. Worth budgeting for it.
How this was read
- The first two digits, 17, are the year: 2017.
- The next two digits, 19, are the week of the year, so about May.
Format: Year and week. Sources: CPSC 2019 A.O. Smith recall (year and week), CPSC 2008 A.O. Smith and State recall (month letters), A.O. Smith Service and Warranty Guide (PDF).
Reading a A.O. Smith serial number
Since about 2008 A.O. Smith serials start with the year and then the week, so 1719 means the 19th week of 2017.
Older units start with letters. A month letter (A is January, I is skipped) is followed by a two-digit year.
About A.O. Smith
- The company traces back to Charles J. Smith’s machine shop, opened in 1874.
- In 2006 A.O. Smith listed water heater plants in Ashland City, Franklin and Cookeville, Tennessee, McBee, South Carolina, Charlotte, North Carolina, Florence, Kentucky, and Renton, Washington, plus Juarez, Mexico, and Stratford, Ontario.
- Since April 2017 Lowe’s has sold A. O. Smith Signature Series water heaters (Signature, Signature Select and Signature Premier) as an exclusive line.
- A.O. Smith dates its glass-lined tank to 1933.
Sources: A. O. Smith History, A.O. Smith buys American Water Heater parent (Contractor, 2006), Lowe's To Exclusively Offer A. O. Smith Signature Series Water Heaters (PR Newswire, 2017), A. O. Smith Introduces New Generation of Signature Series Water Heaters at Lowe's (2021)
Year and week
Used about 2008 to today. Example: 1719106145074
The first two digits are the year and the next two are the week of the year. A letter may come first or in the fifth position; it is a plant code. A CPSC recall notice confirms this reading: "the first four digits represent the year and week of production".
Worked example: 1719106145074 was built Week 19 of 2017 (around May), so it is 9 years, 5 months old as of October 2026.
Sources: CPSC 2019 A.O. Smith recall (year and week), CPSC 2008 A.O. Smith and State recall (month letters), A.O. Smith Service and Warranty Guide (PDF)
Plant letter, month letter and year
Used through June 2004. Example: MK890054977H43
The first letter is the factory, the second letter is the month (A is January, I is skipped), and the next two digits are the year. MK89 means October 1989.
Worked example: MK89-0054977-H43 was built October 1989, so it is 37 years old as of October 2026.
| Letter | Month |
|---|---|
| A | January |
| B | February |
| C | March |
| D | April |
| E | May |
| F | June |
| G | July |
| H | August |
| J | September |
| K | October |
| L | November |
| M | December |
Sources: CPSC 2019 A.O. Smith recall (year and week), CPSC 2008 A.O. Smith and State recall (month letters), A.O. Smith Service and Warranty Guide (PDF)
Month letter and year
Used july 2004 to about 2008, and older State units. Example: L07A071460
The first letter is the month (A is January, I is skipped) and the next two digits are the year. L07 means November 2007.
Worked example: L07A071460 was built November 2007, so it is 18 years, 11 months old as of October 2026.
| Letter | Month |
|---|---|
| A | January |
| B | February |
| C | March |
| D | April |
| E | May |
| F | June |
| G | July |
| H | August |
| J | September |
| K | October |
| L | November |
| M | December |
Sources: CPSC 2019 A.O. Smith recall (year and week), CPSC 2008 A.O. Smith and State recall (month letters), A.O. Smith Service and Warranty Guide (PDF)
1970s series, month letter and year
Used 1970s to early 1980s. Example: 800M7209519
A three-character series code comes first, then the month letter and the year, like 800-M-72-09519 for December 1972.
Worked example: 800-M-72-09519 was built December 1972, so it is 53 years, 10 months old as of October 2026.
| Letter | Month |
|---|---|
| A | January |
| B | February |
| C | March |
| D | April |
| E | May |
| F | June |
| G | July |
| H | August |
| J | September |
| K | October |
| L | November |
| M | December |
Sources: CPSC 2019 A.O. Smith recall (year and week), CPSC 2008 A.O. Smith and State recall (month letters), A.O. Smith Service and Warranty Guide (PDF)
A.O. Smith recalls
Recalls from the U.S. Consumer Product Safety Commission that name A.O. Smith. Whether a unit is included depends on its model and build date; the checker above flags matches.
| Year | Recall | Hazard |
|---|---|---|
| 2018 | A.O. Smith Ultra-Low NOx gas water heaters | The burner screen can tear and the burner can overheat a wood floor. |
| 2018 | A.O. Smith 30-gallon gas water heaters sold at Lowe’s | The flame arrestor can fail and cause a fire. |
| 2008 | A.O. Smith and State 75-gallon gas water heaters | Vent gases can get too hot and start a fire, or leak carbon monoxide into the room. |
| 2005 | A.O. Smith 75-gallon propane water heaters | Soot can build up on the burner and start a fire. |
| 2004 | White-Rodgers controls on propane and convertible gas water heaters | The control can open slowly, so soot builds up on the burner and can start a fire. |