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Cimarron Water Heater Age by Serial Number — Free Lookup

Rheem

Enter the serial number from the rating plate (the silver data sticker on the upper side of the tank; on tankless units it is inside the cover on the right side). Works for Rheem, Ruud and Richmond — many Rheem plates also print the manufacture date directly as "MFG. DATE".

How Old Is Your Cimarron Water Heater?

Cimarron is a private-label brand built by Rheem, so its serial numbers use Rheem's date code: month, then year, in the first four digits after any letter prefix. Enter your serial in the free decoder above for an instant answer, or follow the guide below to read it yourself.

Where to Find the Serial Number

Check the rating plate on the side of the tank — a silver or white sticker, usually in the upper half, that lists the model number and serial number together. The date lives in the serial, not the model number. On older tanks the sticker can fade; a phone photo with the contrast bumped usually makes the digits readable.

How the Cimarron Serial Format Works

Rheem encodes the date as MMYY — month first, then year — in the first four digits after any letter prefix:

Worked example — RH0806B17262:

  • RH = plant code (ignore)
  • 08 = August (month)
  • 06 = 2006 (year)
  • B and the remaining digits = production sequence
  • Result: manufactured in August 2006

Letter prefixes are plant codes. Serials often start with R, RH, RN, RHNG, or a single letter — none of these are part of the date. Skip them and read the first four digits you find. Some very old Cimarron units used week-based formats; if the digits don't decode as a valid month, the decoder says so rather than guessing.

Why Your Cimarron Water Heater's Age Matters

  • Lifespan. Tank water heaters average 8–12 years of service. Past that, internal corrosion makes tank failure — and a flooded floor — far more likely.
  • Condition tells. An old private label is often original equipment from when the house was built; knowing its age tells you whether it's the first thing to replace in a renovation.
  • Replacement planning. A unit past 10 years is on borrowed time. Knowing the date lets you shop for a replacement calmly instead of during an emergency.

Sources

Brand ownership and serial format verified against the InterNACHI water heater dating chart and InspectApedia's Rheem age decoder.

Frequently asked questions

Who makes Cimarron water heaters?
Cimarron is a private-label brand built by Rheem, one of the largest water heater manufacturers in the US. The InterNACHI water heater dating chart groups Cimarron with Rheem production lines, so Cimarron serials carry the same month-year date code as Ruud, Richmond, and GE units.
How do I tell the age of a Cimarron water heater from the serial number?
After any leading letter prefix, the first two digits are the month and the next two are the year. For example, serial RH0806B17262 means August 2006 — month 08, year 06. Letters before the digits are plant codes; the date always follows them.
Where is the serial number on a Cimarron water heater?
On the rating plate — a silver or white sticker on the side of the tank, usually in the upper half, that lists the model and serial numbers together. If it has faded, photograph it and boost the contrast; the first four digits after any prefix are all you need.
Are Cimarron water heaters still sold?
Cimarron was an older private label — most units you will find are 1980s–2000s vintage, often in older homes. The decoding rules are the same regardless of age, though very old units may use one of Rheem's retired formats.
How long does a Cimarron water heater last?
Tank-style units average 8–12 years. If your Cimarron is past 10 years — or an older unit you found in a fixer-upper — plan for replacement before a leak decides for you.