Where to look: Rating label on the tank jacket; on tankless units, the label on the cabinet side; on heat-pump models, the label on the upper body. Read it from the outside. If the label isn’t visible without removing a panel, don’t open the unit; use the installation paperwork or ask the installer.
Decode a Rheem serial number
How to read a Rheem serial number
MMYY… Optional letter prefix (R, RH, RN, RNG or RHNG), then two digits for the month and two for the year: MMYY. Example 1209D01234 = December 2009.
| Example serial | How it reads | Built |
|---|---|---|
1209D01234 | 12 = December, 09 = 2009 | December 2009 |
0721M12345 | 07 = July, 21 = 2021 | July 2021 |
- Rheem’s serial number guide (opens in a new tab) breaks its example 1209D01234 into month (12), year (09), plant line code (D) and a sequence number.
- The label is on the tank jacket of storage heaters, on the side of the cabinet on tankless units, and on the upper body of heat-pump models.
- Some Rheem-built serials start with a short letter prefix such as R, RN, RNG or RHNG, according to InspectAPedia’s Rheem decoder (opens in a new tab). Ruud and Richmond serials use the same month-year digits and have their own entries in the decoder.
Format source: Rheem: how to locate and read your water heater serial number (opens in a new tab); also InspectAPedia: Rheem water heater age decoder (opens in a new tab).
What to do with the date
- Check the warranty. Enter the serial number in the Rheem warranty lookup (opens in a new tab). Coverage depends on the model and the build or installation date.
- Weigh repair against replacement. Age is one factor; leaks from the tank, rusty hot water and repeated failures matter more. See how long water heaters last and the repair-or-replace notes on the main decoder page.
- Troubleshoot by brand. Our Rheem guides cover codes, lights, leaks and no-hot-water problems.
Common questions
My Rheem serial starts with letters. Where is the date?
Skip the letter prefix; the four digits that follow are the month and year. The decoder ignores the common prefixes R, RH, RN, RNG and RHNG; for any other letters, start reading from the first four digits.
Could 0610 be October 2006?
No. Rheem puts the month first, so 0610 is June 2010.
Other brands: Bradford White · A. O. Smith · State · Whirlpool · American Water Heater · Rinnai · all brands