Rheem, Ruud, WeatherKing and Richmond water heaters use a ten-digit serial number that reads in the opposite order from Rheem's own HVAC equipment, and confusing the two produces a wrong month and year both. Rheem's own water-heater serial-number page states the rule directly: the first two digits are the two-digit month of manufacture, the next two digits are the two-digit year, the fifth character is a letter marking the manufacturing plant line, and the remaining five digits are a sequential production number.
A serial reading 0806 in its first four digits was therefore built in August of 2006. This is Rheem's own published convention for water heaters specifically, confirmed on the same official page that gives the location of the data tag, and it is separate from the week-then-year rule this site documents for Rheem's air conditioners, furnaces and heat pumps. Rheem has not published a different water-heater format for any other era, so no older format is described here.
Try it
Decode your own serial number
What this covers
- Rheem, Ruud, WeatherKing and Richmond residential water heaters with a 10-digit serial on the rating label
- Reading the two-digit month from positions 1–2 and the two-digit year from positions 3–4
- The plant-line letter in position 5, which does not affect the date reading
What it does not cover
- ×Rheem, Ruud or WeatherKing HVAC equipment (air conditioners, furnaces, heat pumps), which uses a different week-then-year serial format covered separately on this site
- ×Any Rheem water heater whose serial does not fit the 10-digit pattern
- ×A guarantee that this format extends to commercial-only Rheem water-heating products
Try in this order
0 of 4 completedLocate the data tag
ReversibleCheck the exterior of the tank — commonly on the side, near the top, or on the jacket close to the controls.
Read the first two digits as the month
ReversibleThese are the two-digit month, 01 through 12.
Read the next two digits as the year
ReversibleThese are the two-digit year. A serial starting 0806 means August 2006.
Don't apply this to Rheem HVAC equipment
ReversibleIf the product is an air conditioner, furnace or heat pump rather than a water heater, use this site's separate Rheem HVAC serial-lookup page instead — the digit order is reversed.
Evidence ledger
Sources behind this answer
Where the manufacturer's article stops. Rheem's own page states the month/year/plant reading directly for water heaters. It does not address Rheem's separate HVAC serial format, which this site documents on its own page, linked below.
Exact questions
Questions about Decode a Rheem water heater serial number
Is this the same rule as Rheem's air conditioners and furnaces?+
No. Rheem's HVAC equipment reads week-then-year after a letter; Rheem's water heaters read month-then-year before a letter. Applying one rule to the other product produces a wrong date.
What does the letter in position 5 mean?+
Rheem's own page identifies it as a plant-line code, not part of the date.
Does this cover commercial Rheem water heaters too?+
This page has only confirmed the format for residential tank and hybrid water heaters described on Rheem's own consumer page.
Where do I find the Rheem water heater serial number?+
Look for the rating plate or label on the unit, on the rating plate on the tank. Photograph it before you start, since the label can be hard to read once the appliance is installed.