Rheem water heater age by serial number (also Ruud and Richmond)
A Rheem water heater serial number has ten characters with the date near the front. If it starts with four digits, digits 1 and 2 are the month and 3 and 4 the year: 1209D01234 is December 2009. If it starts with a letter, digits 2 and 3 are the week and 4 and 5 the year. Ruud and Richmond heaters are built by Rheem and are read with the same Rheem rule, labelled as such.
Where the serial number is
The rating plate is a label on the tank jacket; on tankless units it is on the cabinet. Rheem's serial number page has pictures of where to look on each product type. Next to the serial the plate lists the model, the capacity and the energy input, which is useful when you compare the date with paperwork.
Month and year first
In the layout explained on Rheem's website, characters 1 and 2 are the month (01 to 12), characters 3 and 4 are the year, character 5 is a letter for the plant production line and the last five digits are a sequence. Rheem's own example, 1209D01234, reads as December 2009.
Plant letter, then week and year
A 2016 recall that Rheem filed with the U.S. Consumer Product Safety Commission (CPSC 16-177) covered electric tank heaters such as XE40M12EC55U0 and printed serial ranges next to production dates. Those serials begin with a letter followed by nine digits, and the dates only line up if digits 2 and 3 are the week and digits 4 and 5 the year: A0114 is listed as 1 January 2014, A5214 as 21 December 2014 and A0515 as 30 January 2015. The recall shows the letters A, M and Q in first place.
Telling the two layouts apart
Both layouts have ten characters, but the letter sits in a different place. Four digits, a letter and five digits means month and year; a letter followed by nine digits means week and year. A month above 12 in the first layout points to a typing error or an unknown format, never to a guess.
Ruud and Richmond
Both brands belong to Rheem Manufacturing Company: their websites carry Rheem's copyright, and CPSC recall 07-108 lists Rheem, Ruud and Richmond tankless models as products of Rheem Sales Company. Neither brand publishes its own decoding rule. When you choose Ruud or Richmond, the decoder applies Rheem's documented format and says in the result that the rule comes from Rheem documentation, not from a Ruud or Richmond document. If such a date clashes with your paperwork, trust the paperwork.
How to read the plate, step by step
- Copy the ten characters from the plate and choose Rheem, Ruud or Richmond.
- Four digits first: the first two are the month, the next two the year.
- A letter first: digits 2 and 3 are the week, digits 4 and 5 the year; the month shown is the one in which that week begins.
- Check the result against the installation date on your invoice or permit, if you have one.
Serial formats the decoder reads
| Format | How it is read |
|---|---|
| Rheem month + year (MM YY, plant letter, sequence) | Rheem: digits 1-2 are the month and digits 3-4 the year, followed by the letter of the plant production line and a 5-digit sequence. This is the 10-character layout Rheem describes for its water heater rating plates. |
| Rheem plant letter + week + year (P WW YY, sequence) | Rheem, second 10-character layout: a plant letter, digits 2-3 are the week and digits 4-5 the year, followed by a 5-digit sequence. Rheem's own recall filing with the CPSC uses this layout, and its serial ranges line up with the production dates it lists. |
Worked examples
Each serial below is either printed in a source or built by us strictly by the source's rule (marked "by the rule"), and each is an automated test of the decoder. Readings that depend on today's date are as of October 27, 2026.
| Serial | Result | Why |
|---|---|---|
| 1209D01234from a source | December 2009Decoded | The example on Rheem's serial number page: December 2009. |
| 0612F04567by the rule | June 2012Decoded | Month 06, year 12, production line F. |
| A011412345from a source | week 1 of 2014 (about January)Decoded | CPSC recall 16-177 lists serials starting A0114 as made on 1 January 2014 (the last five digits are ours). |
| A521412345from a source | week 52 of 2014 (about December)Decoded | The recall dates serials starting A5214 to 21 December 2014: week 52 of 2014. |
| A051512345from a source | week 5 of 2015 (about January)Decoded | The recall dates serials starting A0515 to 30 January 2015: week 5 of 2015. |
| 1209D01234Ruud (Rheem-built)by the rule | December 2009Decoded | Rheem's own example entered for a Ruud heater: the same reading, labelled as Rheem's rule applied to a Rheem-built brand. |
| 1309D01234by the rule | Does not fit the format | 13 is not a month, so the serial does not fit Rheem's rule (probably a typing error). |
Edge cases and limits
- Rheem prints two year digits. We read them as 2000 or later; when they would point to the 1990s, the decoder says the layout is not documented that early instead of giving a date.
- Older serials that begin with two or more letters, such as RH or RU, are explained only by third-party sites, so they are reported as not confirmed.
- Rheem, Ruud and Richmond tankless heaters imported from Japan between 2004 and 2006 (the subject of CPSC recall 07-108) may follow another layout; Rheem gives no tankless example.
- GE tank heaters from 2003 to 2007 name Rheem as the maker in their manuals, but neither GE nor Rheem explains the GE serial, so GE is not decoded here.
- Rheem and Ruud also run age lookups on their own websites, which send the serial to the manufacturer. This decoder works in your browser and sends nothing.
Brands decoded by inference
- Ruud is a Rheem-built brand, so this result applies Rheem's documented format. The rule comes from Rheem documentation, not from a Ruud document; Ruud does not publish its own decoding rule.
- Richmond is a Rheem-built brand, so this result applies Rheem's documented format. The rule comes from Rheem documentation, not from a Richmond document; Richmond does not publish its own decoding rule.
Questions
Do Ruud and Richmond water heaters use the Rheem serial number format?
They are Rheem-built brands, and the decoder reads them with Rheem's documented format. No Ruud or Richmond document states the rule itself, so those results say that the rule comes from Rheem documentation.
My Rheem serial starts with a letter. Which week does it mean?
Digits 2 and 3 are the week of the year. Week 01 starts on 1 January, so week 05 falls at the end of January and week 52 in late December, which is how Rheem's recall listed them.
Do Rheem air conditioners and furnaces use the same layout?
No. Rheem's serial number page covers water heaters only. Rheem's HVAC parts lists describe a different layout: a plant letter, then the week and the year of production.
Related pages
- Bradford White: Bradford White codes the year and the month as letters.
- A. O. Smith family: A. O. Smith brands put the year first and then the month or the week.
- All water heater brand families: Every brand family we decode, and the brands we do not decode yet with the reason.
- Where to find the data plate: Where the serial number sits on each type of equipment and how to copy it without mistakes.
- Service life estimates: What ENERGY STAR publishes about typical ages, and what kind of number each figure is.
Sources
Every rule on this page comes from the documents below, published by the manufacturer or a U.S. government agency. The date is when we last checked each one.
- How to locate and read your Rheem water heating serial numbers Rheem Manufacturing Company. Checked .
- Rheem recalls to repair water heaters (CPSC recall 16-177, 26 May 2016) U.S. Consumer Product Safety Commission. Checked .