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Rheem water heater age decoder.
Enter the serial number from the rating label to see the month and year it was made, using the month and year digits Rheem describes.
Serial number
Result
Rheem's water heating rating labels carry a ten-character serial number, and the first four characters are the date: two digits for the month and two for the year. Enter the serial and this page reads those digits the way Rheem describes them and gives the manufacture date and an approximate age. It does not look up warranty status or the model.
How the code works
Rheem shows its layout with the example 12 09 D 01234 and labels the parts: month manufactured (12), year manufactured (09), plant line code (D) and a consecutive serial number (01234). Read together, 1209 is December 2009. Rheem says the serial on all its water heating product rating labels has ten characters, which is why this page accepts spaces and dashes but flags a serial of another length. The plant line code and the consecutive number identify where and in what order the unit was built; they do not change the date.
The page reads the two year digits as 20 followed by those digits, so 09 is 2009 and 25 is 2025. Rheem's page does not state the century. A serial that would land in the future is rejected, and a unit from the 1990s with the same layout would be misread as the 2000s, so treat a result that disagrees with the tank's obvious age with suspicion.
Worked examples
1209D01234. Month 12, year 09: December 2009. In early November 2026 the tank is about 16.9 years old, well past the 8 to 12 year range one manufacturer, Reliance, gives as typical for a water heater.
0517B04321. Month 05, year 17: May 2017, about nine and a half years old.
1399A00001. The month digits 13 are not a month, so this page says the serial does not follow the published scheme. Check that the digits were copied correctly, or whether the label shows a different layout.
Limits
- Manufacture is not installation. Warranty periods usually start from installation or registration, not from the date in the serial. Use Rheem's warranty tool on its site for that.
- Layout shown is for water heating labels. Rheem's heating and cooling equipment has its own pages and this page does not decode it.
- Other labels. Older labels, and units sold under other names, may use different layouts. If the first four characters are not digits or the first two are not a month, do not rely on the result.
- Brand, not group. This applies Rheem's published description to Rheem water heating labels only. It is not assumed to apply to any other brand.
If the tank is old, the recovery time calculator shows how long a tank takes to reheat and the tank size calculator helps size a replacement. For other makers see the serial number guide by brand, or the Bradford White decoder, which uses letters instead of digits.
FAQ
What do the first four digits of a Rheem water heater serial number mean?
Rheem labels the first two as the month manufactured and the next two as the year manufactured. In its example 12 09 D 01234, 12 and 09 give December 2009.
How long is a Rheem serial number?
Rheem says the serial number on its water heating product rating labels has ten characters: month, year, a plant line code and a five-digit consecutive number in its example.
What is the letter in the middle of my Rheem serial number?
Rheem calls it the plant line code. It identifies where the unit was built and does not change the date.
Can I tell the warranty status from the serial number?
Not from the digits. The date is the date of manufacture. Rheem has a warranty verification tool on its website that takes the serial number.
Does this work for Ruud, Richmond or other brands?
This page only applies what Rheem publishes for Rheem water heating labels. It makes no claim about other brands, so check each maker's own page.
Why does the page read the year as 20 followed by two digits?
Rheem's page gives a two-digit year without a century. This page assumes the 2000s, rejects any date in the future, and cannot tell a 2000s unit from an older one that used the same layout.
Sources
Each page was opened and read on 2026-11-01. Manufacturers can change these pages without notice.
- Rheem: How to locate and read your Rheem water heating serial numbers: the ten-character layout and the month, year, plant line code and consecutive-number fields, with the 12 09 D 01234 example. Read 2026-11-01.
General information only
This page is general information, not professional plumbing, safety or warranty advice. A serial number shows when a unit was made, not when it was installed or whether a warranty still applies. Confirm warranty status with the manufacturer and have a licensed plumber assess any unit you are unsure about. Everything runs in your browser; nothing you enter is sent anywhere.