Rheem water heater date code: month and year in the first four digits
Rheem says the serial number on its water heating rating labels has ten characters. The first two give the month of manufacture and the next two give the year.
Manufacture date, not install date or warranty status. A date code tells you when the maker built the unit. It does not tell you when it was installed, whether any warranty applies, or what condition the unit is in.
Rheem's layout
| 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 |
Read that way, Rheem's example serial 1209D01234 was built in December of year 09. Rheem's page is about its water heating products. We have not checked Rheem air conditioners or furnaces.
Read your code
Limits of the two-digit year
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 to find the serial
Rheem's page says the serial number is on the product rating label. Copy it exactly, including any letters.
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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