Sometimes, finding your water heater model number can be tricky. But, all water heaters have a Rating Plate that lists important data such as the model and serial numbers, manufacturing company’s name, length of warranty, wattage of elements installed (on electric models), gallon capacity, input BTU rating (gas models), and more.

Rheem Water Heater Model Numbers

New Rheem water heaters have an easy to understand rating plate. It includes the manufacture date, as well as information on the size and capacity.

On older models, you can determine the age of your unit by decoding the water heater serial number. Some manufacturers, including Rheem, made it easy by incorporating the month and year built into the first 4 digits of the serial number. For instance, the picture below shows that this Rheem water heater was manufactured in December of 1991 (1291). Other manufacturers use different formats, but in a similar fashion.

rheem model number

Let’s decode the above rating plate: This is water heater model number 21V50-2, serial number 1291A39968, manufactured in December of 1991, 50 gallons, 36000 BTU’s per hour, and is set to work with natural gas only. The other info you see relates more to service technicians, and shouldn’t be needed by the average homeowner.

The picture below shows the entire Rheem rating plate. This 50 gallon electric tank was built in August of 1984, and came equipped with 4000 watt elements

The picture below shows the entire Rheem rating plate. This 50 gallon electric tank was built in August of 1984, and came equipped with 4000 watt elements


A.O. Smith Model Numbers

AO Smith rating plates look a little different, but have all the same info. Their date decoding is a little different.


AO Smith puts the year first (1991), and the month second (07, or JULY). It’s a little harder to find the info on the AO Smith plate, but it’s all there!

aosmith upclose

Bradford White Model Numbers

The Bradford White rating plate is the most difficult to decode. To find the age of a Bradford White tank, you have to understand their coding. The year of manufacture is noted by the first letter of the serial number, the month is the second letter. The decoding is based on the following format:
Year Decoder: G = 1990; H = 1991; J = 1992; K = 1993; L= 1994; M= 1995; N= 1996; P= 1997; S= 1998; T= 1999; W= 2000; X= 2001; Y= 2002; Z=2003; A= 2004; B=2005; C=2006; D=2007
Month Decoder: A= JAN; B=FEB; C=MAR; D= APR; E=MAY; F= JUNE; G=JULY; H= AUG; J= SEPT; K=OCT; L= NOV; M= DEC.

The example rating plates is on a tank made in June 2002.

bradford white model number

Above is a close up of the Bradford White rating plate. This is a 40 gallon electric water heater, model number MI40L6DS13, manufactured in June of 2002. It comes equipped with 4000 watt elements. Note the “Maximum Watts” at 4000, this means the tank was built to operate in the “non-simultaneous” mode, meaning only one element will energize at a time (standard for residential water heaters). It is designed to operate with a maximum of 150 PSI water pressure, but was tested to 300 PSI at the factory for your safety.

American Water Heater Model Numbers

American water heater rating plate, with close up below.

american water heater rating plate

American’s format puts the year first, then the week the tank was built. In this example, the tank was made in the 17th week of 1998.

american water heater close
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