Rheem water heater date code: month and year in the first four digits
Rheem's serial number page says the serial number on its water heating rating labels has 10 characters. The first two give the month of manufacture and the next two give the year. Rheem's own example, 1209D01234, reads as December of year 09.
How Rheem lays out the serial
| Characters | Rheem's example | Meaning (Rheem's label) |
|---|---|---|
| 1–2 | 12 | Month Manufactured |
| 3–4 | 09 | Year Manufactured |
| 5 | D | Plant Line Code |
| 6–10 | 01234 | Consecutive serial number |
Rheem's serial rule puts the month first, then the year. Rheem's page covers its water heating products. This rule is not confirmed for Rheem air conditioners or furnaces.
What your serial says
Which century a two-digit year means
The year is two digits. Our reader reads 09 as 2009, as Rheem's example does, and switches to 19xx only when 20xx would be in the future. If that reading does not fit what you know about the unit, trust the label and the maker over our reader.
Where the serial is
Rheem's page says the serial number is on the product rating label. Copy it exactly, including any letters.
Sources
- Rheem, How to locate and read your Rheem water heating serial numbers: https://www.rheem.com/how-to-locate-and-read-your-rheem-water-heating-serial-numbers/, accessed 2026-10-27