How old is my A.O. Smith water heater?
Serial number age decoder for A.O. Smith tank water heaters: 4 format eras, the decode rule in plain English, transcribed tables, and the official lookup.
Type the serial from the data plate, not the model number. Nothing is sent anywhere; the tables are in this page.
Format example: 1210A002243
- A.O. Smith water heater serial numbers in the 2008 to present format encode the year as digits 1-2 (YY) after optional leading S and the week as digits 3-4 (source: building-center.org).
- Example: serial 1210A002243 decodes to week 10 of 2012.
- A.O. Smith water heater serial numbers in the before 2010 format encode the year as digits 2-3 and the month as letter 1 (A=Jan..) (source: building-center.org).
- Example: serial E07A135491 decodes to May 2007.
- A.O. Smith water heater serial numbers in the before 2008 format encode the year as digits 3-4 and the month as letter 2 (A=Jan..) (source: building-center.org).
- Example: serial AF04A093001 decodes to June 2004.
- A.O. Smith's official lookup at hotwater.com returns warranty status.
Format eras
- before 2010 VERIFIED
A##A######digits 2-3 - 2008 to present VERIFIED
####A######digits 1-2 (YY) after optional leading S - before 2008 VERIFIED
AA##A######digits 3-4 - 1970 to 1979 VERIFIED
A##-A-##-######2 digits between hyphens (78)
How to read the serial
before 2010 formatVERIFIED
Shape A##A###### · example E07A135491 · confidence medium
- Year
- digits 2-3
- Week or month
- month = letter 1 (A=Jan..)
| Month code | Month |
|---|---|
| A | January |
| B | February |
| C | March |
| D | April |
| E | May |
| F | June |
| G | July |
| H | August |
| I | September |
| J | October |
| K | November |
| L | December |
Example: serial E07A135491 decodes to May 2007.
2008 to present formatVERIFIED
Shape ####A###### · example 1210A002243 / S1318 F000046 / 1836111786352 · confidence high
- Year
- digits 1-2 (YY) after optional leading S
- Week or month
- week = digits 3-4
- Plant
- letter after the 4 date digits (unpublished)
Example: serial 1210A002243 decodes to week 10 of 2012.
before 2008 formatVERIFIED
Shape AA##A###### · example AF04A093001 / GG03-1495366-S29 · confidence medium
- Year
- digits 3-4
- Week or month
- month = letter 2 (A=Jan..)
- Plant
- letter 1
| Month code | Month |
|---|---|
| A | January |
| B | February |
| C | March |
| D | April |
| E | May |
| F | June |
| G | July |
| H | August |
| I | September |
| J | October |
| K | November |
| L | December |
Example: serial AF04A093001 decodes to June 2004.
1970 to 1979 formatVERIFIED
Shape A##-A-##-###### · example A20-H-78-015482 · confidence medium
- Year
- 2 digits between hyphens (78)
- Week or month
- month = letter between hyphens (H=Aug)
| Month code | Month |
|---|---|
| A | January |
| B | February |
| C | March |
| D | April |
| E | May |
| F | June |
| G | July |
| H | August |
| I | September |
| J | October |
| K | November |
| L | December |
Example: serial A20-H-78-015482 decodes to August 1978.
Where the data plate is on a water heater
The rating plate is a large label on the side of the tank near the top or beside the control. The serial is printed on it, often beside the model number and the ANSI standard line.
General guidance, not brand-specific: the owner's manual or the installer can point to the exact spot. See the data plate guide.
For scale only: the InterNACHI Standard Estimated Life Expectancy Chart for Homes lists Water Heater (conventional) at 6 to 12 years of expected service (nachi.org). That chart is a guideline, not a prediction for your unit.
Open the official A.O. Smith lookup takes serial or reference number; returns warranty status; URL verified live
This site is a reference built from published tables. The manufacturer's own lookup wins whenever the two disagree.
Sources
- https://www.building-center.org/a-o-smith/
- https://www.hotwater.com/support/warranty-verification.htmlofficial
Frequently asked questions
How do I tell the age of a A.O. Smith water heater from the serial number?
In the 2008 to present format the year is digits 1-2 (YY) after optional leading S and the week as digits 3-4. Example: serial 1210A002243 decodes to week 10 of 2012.
Where is the serial number on a A.O. Smith water heater?
On the data plate. The rating plate is a large label on the side of the tank near the top or beside the control. The serial is printed on it, often beside the model number and the ANSI standard line.