How Old Is My Water Heater?

Determining how old your water heater is should be a straightforward and easy task. But unfortunately, you may feel like you're decoding a cipher! But once you know what you're looking for, and you have the key, you may find determining your water heaters age is actually kind of fun.

Well, maybe fun isn't the word for it, but it's really not too hard. This article will give you the tools you need to determine the age of your water heater. Each manufacturer uses a different method, so we'll take a look at some of the most popular water heater brands.

How to Determine the Age of Your Water Heater

Newer water heater models often list a build date on the information sticker attached to the side of the tank or tankless unit.

Unfortunately, older models can be a bit more challenging and each manufacturer uses a different system to indicate the age of their water heaters.

You'll need the brand name and the serial number to determine the age of your water heater. This information is listed on the information sticker on the side of the tank.

The brand name will tell us how to decipher the serial number in order to determine the month and year of construction.

Keep in mind, this is the build date, not the date the water heater was installed and went into service. Although, typically the dates are relatively close.

Rheem Water Heater Age

Rheem is a major player in the water heater industry, they also offer an easy method on their website to find the build date. Simply enter your water heater's serial number and the age of your water heater will be displayed.

However, if you prefer to figure it out on your own, they use 5 different formats:

Style 1: ****0884******

• The serial number will begin with: R; RN; RNG; RHNG; etc.
• First two numbers are the month 
• Numbers 3 and 4 are the year
• In this example, the water heater was built in August of 1984

Style 2: *1415*****

• First two numbers are the week
• Numbers 3 and 4 are the year
• In this example, the water heater was built the 14th week of 2015 

Style 3: *1114***********

• First two numbers are the month
• Numbers 3 and 4 are the year
• In this example, the water heater was built in November of 2014

Style 4: ****0804*******

• The serial number will begin with: R; RN; RNG; RHNG; etc.
• First two numbers are the month
• Numbers 3 and 4 are the year
• In this example, the water heater was built in August of 2004

Style 5: 05.05-******

• This is a tankless water heater
• First two numbers are the year
• Numbers 3 and 4 are the month
• In this example, the water heater was built in May of 2005

Style 6: *1814*****

• The serial number will begin with: R; RN; RNG; RHNG; etc.
• First two numbers are the week
• Numbers 3 or 4 are the year
• In this example, the water heater was built the 18th week of 2014

Ruud

Rheem also produces and sells water heaters under the Ruud name.

If you own a Ruud water heater you can follow the Rheem serial styles above.

Bradford White Water Heater Age

Determining the age of a Bradford White Water Heater requires a code, and although it's not that hard, it is more complex than it needs to be. 

Style 1: DG*******

• The first letter represents the production year (see below)
• The second letter represents the production month (see below)
• Using the information below, this water heater was built in July of either 1987 or 2007.

Determining the Year of Production

Bradford White uses a 20-year rotating letter system to indicate the year the water heater was manufactured. 

* Bradford White did not use the letters: I, O, Q, R, U, or V 

* In January of 1997 Bradford White had a computer error. These water heater's serial numbers started with the digits OA

Determining the Month of Production

This chart will help you decipher the production month:

* Bradford White did not use the letter: I

State Water Heater Age

In 1996 State became the world's largest producer of water heaters and were producing an average of 10,000 units a day. However, in 2001 they were acquired by AO Smith.

State uses four different styles of serial numbers:

Style 1: 1210******* or *1318*******

• First two numbers are the year
• Numbers 3 and 4 are the week
• In these examples, the water heaters were built on the 10th week of 2012 / 18th week of 2013

Style 2: H76******* or M07*******

• Starting letter is the month (see below)
• Numbers 2 and 3 are the year
• In these examples, the water heater was built in August of 1976 / December of 2007

Style 3: A05*******

• Both the month and year are shown in a coded format (see below)
• In this example, the water heater was built in January of 2005

There were a few models built in 2004 that use the following format:

MD04*******

• The first letter is the factory code
• The second letter is the month
• The 3 and 4th numbers are the year
• In this example, the water heater was been manufactured in April of 2004

Style 4: 1735*********

• The first two numbers are the year 
• The third and forth numbers are the week
• In this example, the water heater was manufactured the 35th week of 2017

American Water Heater Age

American Water Heaters was founded in 1996, and was operated under the Canadian parent of company GSW from 2002-2006. In April of 2006, they were acquired by AO Smith and are currently operating as a subsidiary of AO Smith.

American Water Heaters have distributed a long list of brand names, including: Ace Hardware; American Hardware; Craftmaster; Lowes; Neptune; Prestige Water Heaters; Standard; U.S. Craftmaster; Whirlpool Brand Water Heaters; among others.

There are two styles of serial numbers used:

Style 1: 0503* *****

• First two numbers are the year
• Numbers 3 and 4 are the month
• In this example, the water heater was built in March of 2005

Style 2: 1924*********.

• First two numbers are the year 
• Numbers 3 and 4 are the week
• In this example, the water heater was built the 24th week of 2019

AO Smith Water Heater Age

The AO Smith company has been around since 1874, but it didn't begin producing residential water heaters until 1939. AO Smith has been a leader of water heater technology, including the development of the glass lined tank, which is now an industry standard.  

Although water heaters are sold under their own name, AO Smith also manufactures models under the following brands: GSW; John Wood; Whirlpool; US Craftmaster; American; State; Reliance; Kenmore; Takagi; and Lochinvar.

AO Smith uses four primary styles of serial numbers:

Style 1a: 1210 *******

• First two numbers are the year 
• Numbers 3 and 4 are the week
• In this example, the water heater was built on the 10th week of 2012

Style 1b: *1318 *******

• The second and third digits are the year
• digits 4 and 5 are the week
• In this example, the water heater was built on the 18th week of 2013

Style 1c: 1836*********

• First two numbers are the year
• Numbers 3 and 4 are the week
• In this example, the water heater was built on the 36th week of 2018

Style 2: *F04******* 

• The first * represents the factory code, the letter that follows represents the month (see below). In July of 2004 AO Smith stopped using the factory designation and the serial number appeared like this: F04******* 
• Numbers 3 and 4 are the year. (After July of 2004 numbers 2 and 3 represent the year)
• In this example, the water heater was built in June of 2004

Style 3: *G03-*******-***

• The first * represents the factory code, the letter that follows represents the month (see above). In July of 2004 AO Smith stopped using the factory designation and the serial number appeared like this: G03-*******-***
• Numbers 3 and 4 are the year. (After July of 2004 numbers 2 and 3 represent the year)
• In this example, the water heater was built in July of 2003

Style 4: E07*******

• First letter is the month (see below)
• Numbers 2 and 3 are the Year
• In this example, the water heater was built in May of 2007

GE Water Heater Age

GE water heaters use four different serial number styles:

Style 1: 1108******

• The first 2 numbers are the month
• Numbers 3 and 4 are the year
• In this example, the water heater was built in November of 2008

Style 2: 0902*******

• The first 2 numbers are the month
• Numbers 3 and 4 are the year
• In this example, the water heater was built in September of 2002

Style 3: GENG 0601******

• The first 4 letters are an abbreviation for GE Natural Gas
• The next 2 numbers are the month
• Numbers 3 and 4 are the year
• In this example, the water heater was built in June of 2001

Style 4: **0197******

• The 2 numbers that follow the first two digits indicate the month
• The next 2 numbers are the year
• In this example, the water heater was built in January of 1997

Navien Water Heater Age

Navien uses four different serial number styles for their tankless water heaters:

Style 1: *****11527*****

• The 6th and 7th digits represent the year
• The 8th digit represents the month
• The 9th and 10th digit represent the day
• In this example, the water heater was built on May 27, 2011

Style 2: *****14********

• The 6th and 7th digit represents the year
• In this example, the water heater was built in 2014

Style 3: ****-20081208-****

• The 5th thru 8th digits represent the year
• The 9th and 10th digits represents the month
• The 11th and 12th digit represent the day
• In this example, the water heater was built on December 8, 2008

Style 4: ****-2008-114-1014

• The 5th thru 8th digits represent the year
• The 9th digit represents the month
• The 10th and 11th digit represent the day
• In this example, the water heater was built on January 14, 2008

Noritz Water Heater Age

Noritz uses a very straight forward method in labelling the build date of their tankless water heaters.

There is only one style:

Style 1: 2005.06-******

• The first 4 digits represent the year
• The 5th and 6th digits represents the month
• In this example, the water heater was built in June of 2006

Rinnai Water Heater Age

Rinnai uses two different styles to indicate when their tankless water heaters were built.

Style 1: BL. **-******

• The 1st letter represents the year (see below)
• The 2nd letter represents the month (see below)
• In this example, the water heater was built in November of 2010

Style 2: 04. 03-*****

• Digits 1 and 2 represent the year
• Digits 3 and 4 represent the month
• In this example, the water heater was built in March of 2004