Rheem · Ruud · HVAC & Water Heaters · MMYY Format
Rheem Serial Number Age Lookup
Find your Rheem water heater or HVAC manufacture date.
Rheem and Ruud encode the production month and year directly into the date block following the plant prefix letter. Enter your serial number below for instant informational decoding.
Rheem Date Code Decoder
Enter your Rheem serial number.
Locate the rating plate on your Rheem or Ruud residential water heater, gas furnace, heat pump, or AC condenser to decode its production date.
Enter your Rheem serial number above
Type the serial number from your equipment rating plate to decode the production month, manufacture year, and estimated age.
How Rheem Encodes Age in Serial Numbers
On modern Rheem and Ruud heating, cooling, and water heating units, the date code is commonly placed in a 4-digit numeric block (MMYY) immediately following an initial factory identifier letter:
Example: Serial Number M041912345
- Prefix Letter (
M): Manufacturing plant code (e.g., Montgomery, Alabama facility). - Next Two Digits (
04): Manufacture month = 04 (April). - Following Two Digits (
19): Manufacture year = 2019. - Remaining Characters (
12345): Sequential production tracking number.
Where to Find the Serial Tag on Rheem Units
Rheem Tank Water Heaters
Affixed on the exterior jacket of the water tank near the upper thermostat access door, rating label, or temperature and pressure (T&P) relief valve.
Rheem Gas Furnaces
Turn off electrical power, remove the upper door, and locate the rating sticker on the inner cabinet sidewall near the burner manifold.
Rheem AC Condensers & Heat Pumps
Located on the outer metal jacket near the service panel, electrical line entry, or refrigerant valve access ports.
Rheem Tankless Water Heaters
Affixed on the front metallic cover or the lower left side of the wall-mounted chassis.
Frequently Asked Questions
How do I decode a Rheem serial number to find the age?
In standard Rheem and Ruud serial numbers, look after the initial manufacturing plant letter. The next two digits represent the month (01 for January through 12 for December), and the subsequent two digits represent the year of manufacture. For example, in serial M041912345, '04' denotes April, and '19' denotes 2019.
Does this serial decoder work for Rheem water heaters?
Yes. Rheem and Ruud residential tank water heaters (gas and electric) follow the same 4-digit date block (MMYY) directly following the factory prefix letter.
Where is the serial number located on a Rheem water heater?
On Rheem residential water heaters, the rating sticker is affixed on the front or side of the tank body, typically near the thermostat access panel or temperature/pressure relief valve.
Disclaimer: This HVAC and water heater serial lookup tool provides an informational estimate based on Rheem Manufacturing Company date-coding documentation and third-party industry records compiled by the Building Intelligence Center. Always verify the serial number directly from the unit rating plate. Never attempt gas valve, water heater tank, or refrigerant servicing yourself; always consult a licensed plumber or HVAC contractor.