Determining water heater age date from serial numbers by Final Analysis Home Inspections in Virginia beach, Chesapeake, Suffolk, and Portsmouth Virginia, Va..
| Determining water heater age. |
Related article: Also see "How big should your water heater be" at our Home Inspection news blog.
As home inspectors it's important to be able to decipher the age from the water heater manufacturers serial numbers so we can report aging conditions and tell you when you can expect to replace them because a water heaters service life is approximately 13-18 years.
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.
You can determine the age of the water heater by de-coding the serial number. Some manufacturers make 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.
Let's decode the above rating plate: This is a model 21V50-2, serial number 1291A39968, manufactured in December of 1991, 50 gallons, 36000 BTU's per hour, and it 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 de-coding 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.
Below 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 this 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 (a Federal Standard!).
Water Heater serial number chart Back to Tech Library
| Manufacturer | Trade name | Where to look | How to decode | Example |
| American |
ACE, American, American Hardware, America's Best, Apex, Aqua Temp, AquaTherm, Aquamatic, Best, Best Deluxe, Champion, Craftmaster, De-Limer, Deluxe, Eagle, The Earl's Energy Conservation Water Heater, The Earl's Energy Saver Plus, Envirotemp, Four Most, Hotmaster, Hotstream, King-Kleen, King-Line, Master Plumber, Nationaline, Neptune, Penquin, Premier Plus, Premier Plus Self Cleaning Prestige, ProLine and ProLine Plus, Quaker, Quick-Flo, Raywall, Revere, Riveria, Sands, Sentinal, Servi-Star, Shamrock, Special Deluxe, Standard, Super Eagle, Super-Flo, Supreme, Sure-Fire, Thoro-Clean, Tru-Test, Tru Value, U.S. Supply, Whirlpool, XCL Energy Saver |
Serial # – 1st 4 digits | Serial # – 1st 4 digits | 8906xxx = made in the 6th week of the year 1989 |
| A.O. Smith Water Products | National, A.O. Smith, Glascote, Perma-Glas | Serial # – 2nd, 3rd, 4th characters |
2nd
position (letter) = month (A being January through M being December) 3rd & 4th position (numbers) = year |
AJ89xxx = made in October (J) of 1989 |
| Apollo Comfort Products | See State Industries | |||
| Bradford-White | Bradford White, JetGlas | Serial # – 1st 2 letters |
1st
letter = year starting with A as 1984, 2nd letter = month with January (A) through December (M) |
JMxxx = made in the year 1992 (J) in the month of December (M) |
| Crispaire | E-tech | |||
| GSW Water Heating | John Wood, GSW, Moffat, Superflue, Medal | Serial # – 1st 4 digits |
1st
& 2nd number = year,
3rd & 4th number = month |
8901xxx = made in the year 1989 in the first month, January |
| Heat Transfer Products | Heat Transfer | |||
| Lochinvar | Energy Saver, Golden Knight, Knight | |||
| Marathon | Marathon | Serial # – 1st 4 digits |
1st
& 2nd digit = month,
3rd & 4th digit = year |
0189xxx = made in the year 1989 in the first month, January |
| Maytag | Maytag | |||
| Rheem | Aqua Therm, General Electric, Hotpoint, Professional, Rheem, Vanguard, Western Auto | Serial # – 1st 4 digits |
1st
& 2nd digit = month,
3rd & 4th digit = year |
0189xxx = made in the year 1989 in the first month, January |
| Richmond | Serial # – 1st 4 digits |
1st
& 2nd digit = month,
3rd & 4th digit = year |
0189xxx = made in the year 1989 in the first month, January | |
| Ruud | Professional, Ruud | Serial # – 1st 4 digits |
1st
& 2nd digit = month,
3rd & 4th digit = year |
0189xxx = made in the year 1989 in the first month, January |
| Sears, Roebuck and Co. | Kenmore | |||
| State Industries | State | Serial # – 1st 3 characters | first letter = month (A being January through M, being December), 2nd and 3rd position (numbers) = year | J89xxx = made in October of 1989 |
| Summit Manufacturing Mortex | Sun Therm | |||
| U.S. Craftsmaster |
Ace, American Hardware, America's Best, Apex, Aqua Temp, Aqua Therm, Aquamatic, Best, Best Deluxe, Craftmaster, De-Limer, Deluxe, Eagle, The Earl's Energy Conservation Water Heater, The Earl's Energy Saver Plus, Envirotemp, Four Most, Hotmaster, Hotstream, King-Kleen, King-Line, Master Plumber, Nationaline, Neptune, Penquin, Prestige, Pro-Line, Pro-Line Plus, Quaker, Quick-Flo, Raywall, Revere, Riviera, Sands, Sentinal, Servistar, Shamrock, Special Deluxe, Standard, Supereagle, Super-Flo, Supreme, Sure-Fire, Thoro-Clean, True-Test, Tru Value, U.S. Craftmaster, U.S. Supply, Whirlpool, XCL Energy Saver |
Serial # – 1st 4 digits |
1st 2 digits = year 2nd 2 digits= week |
8924xxx = made in the 24th week of the year 1989 |
| Vaugn Manufacturing Corp. | Sepco, Hydrohot, D.W. Whitehead |