How to find water heater model numbers and rating plates

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 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 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 water heater was manufactured in December of 1991 (1291). Other manufacturers use different formats, but in a similar fashion.

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

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!

American water heater rating plate, with close up below.

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.
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.

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.

You should always look for this information on your water heater before making any important decisions or purchases. You should always have a professional look at the rating plate also to verify the information.

When calling in for a estimate the information you provide from the data plate will be the only thing that we will be able to go by. The location of the water heater, garage , basement, attic, crawlspace, etc. will also be asked to provide a accurate qoute .