How to Determine Your Water Heaters Age

Updated
Categories Water Heating
Do you know how old your water heater is? Here’s how to find out.

Is your water heater beginning to look like an ancient artifact? Or perhaps you’ve moved house and are wondering how long the inherited unit may last? Then it’s probably a good idea to figure out how old your water heater really is.

We’ll walk you through some of the leading brands and manufacturers, and give you a handy guide on how to gauge the age. So let’s get started.


How to Determine Water Heater Age

Determining water heater age is simple on most newer models — the installation date is generally recorded on the information sticker. On older models, however, it’s likely you’ll need to do some detective work.

You may want to start by decoding the serial number — find the details toward the side of the heater. It’s usually placed nearby the energy guide or warning labels.

The serial number holds two crucial details: the month and year of construction. But this is where it gets a little tricky. Manufacturers tend to use different patterns or formats so you’ll have to find your specific manufacturer or brand in order to do this.

To help you decipher your serial number, we’ve put together a guide plus examples from multiple brands and manufacturers.

A.O. Smith

A.O. Smith uses a very basic system which should be straightforward to figure out.

For their older, pre-1997 models, they state the year and week within the first four numbers (1). For example, YYWWxxxxxx. Current models use the same sequence.

For models pre-2008, you should see a number followed by a letter ranging from ‘A’ to ‘M’ (excluding ‘I’). ‘A’ equals January and ‘M’ equals December. The two following numbers indicate the year.

Included brandsExamples of serial numbers
A.O. Smith

PermaGlas

Glascote

Example one: 9808****** (1998, week eight)

Example two: *F06******* (June 2006)

Example three: 1617******* (2016, week 17)

Rheem

Rheem also adopts a simple approach for their different brands. Their newer models, (constructed after 2000) are identified by the month, then the year of manufacture.

In the first example below, we can see the first and second digits are the month. The third and fourth are the year (2).

However, if you look at example two, you’ll notice the numerical order has changed slightly — instead of being the first four digits it’s displayed as the third to sixth. Rheem sometimes presents the key dates in this alternative way.

For their older pre-1999 models, Rheem used weeks instead of months (as shown in example two).

Included brandsExamples of serial numbers
Rheem

Richmond

Vista Therm

Aqua Therm

Energy Master

Lowe’s

Intertherm & Miller

Citation

ABS

Mainstream

Cimarron

Servi-Star

Van Guard

True Value

Ruud

Coast to Coast

Montgomery Ward

Example one: 1110****** (November 2010)

Example two: **1298****** (week 12, 1998)

Bradford White

Instead of using numbers, Bradford White uses two letters. The first indicates the year and the second signifies the month (3).

Year (1st letter)Month (2nd letter)
S = 2018

P = 2017

N = 2016

M = 2015

L = 2014

K = 2013

J = 2012

H = 2011

G = 2010

F = 2009

E = 2008

D = 2007

C = 2006

B = 2005

A = 2004

Z = 2003

Y = 2002

X = 2001

W = 2000

T = 1999

S = 1998

P = 1997

N = 1996

A = January

B = February

C = March

D = April

E = May

F = June

G = July

H = August

J = September

K = October

L = November

M = December

Included brandsExamples of serial numbers
Bradford White

Jetglas

Example one: DG******* (July 2007)

Example two: NK******* (October 1996)

American Water Heater

Because American water heaters are, as of 2001, a subsidiary of A.O. Smith, they now use an identical serial numbering system. If you look at our examples below, the first one is a pre-2000 and the second is pre-2008.

In example one, they’ve referenced the year as the initial two digits. The next two figures relate to the week number.

In example two, we see a system consisting of the letters ‘A’ to ‘M’, excluding ‘I’, to represent the month. The third and fourth numbers indicate the year.

Included brandsExamples of serial numbers
American Water Heater

Champion

Riviera

Aquamatic

Aqua Therm

Raywall

Best Deluxe

King-Line

Whirlpool

Environtemp

Deluxe

Prestige

Sentinel

Proline

Proline-Plus

Aqua Temp

Premier

Nationaline

King-Cleen

Revere

Apex

Example one: 9510****** (1995, week 10)

Example two: *E05******* (May 2005)

State Industries

For State Industries, we’ll show you three examples.

They have two general formats — one using only numbers, and another using letters and numbers. For the first example, numbers one and two represent the year, and numbers three and four indicate the week.

In our second and third example, State Industries use the same code structure — letters to indicate the month and numbers for the year. However, the format of the third is slightly different — it has an extra non-relevant number in front of the date sequence.

For the letters, they use ‘A’ to ‘M’ (excluding I) — ‘A’ being January and ‘M’ December. Then the two following numbers indicate the year of production. For example, 06 equals 2006.

Included BrandsExamples of serial numbers
State

Kenmore

Freedom

Freedom/Nipsco

Ambassador

Ace

Barnett

Crosley

Century

Nationaline

President

Energy Stretcher

Thermo-Ki

Regency

Reliance

Mission

Example one: 1210******* (2012, week 10)

Example two: E03******* (May 2003)

Example three: *E03****** (May 2003)

Lochinvar

Lochinvar’s system is similar to Bradford White’s — they use letters for the month and year (4). It goes like this:

Year (1st letter)Month (2nd letter)
A = 2004

B = 2005

C = 2006

D = 2007

E = 2008

F = 2009

G = 2010

H = 2011

J = 2012

K = 1993

L = 1994

M = 1995

N = 1996

P = 1997

S = 1998

T = 1999

W = 2000

X = 2001

Y = 2002

Z = 2003

A = January

B = February

C = March

D = April

E = May

F = June

G = July

H = August

J = September

K = October

L = November

M = December

Included BrandsExamples of serial numbers
Lochinvar

Knight

Golden Knight

Energy Saver

Example one: PA******* (January 1997)

Example two: XF******* (June 2001)

Navien

This manufacturer takes a totally different approach. On newer models, you’ll see four numbers followed by a single letter. After this letter, there’s a number indicating the year of production followed by another letter.

On older models, Navien simply put the year after the first four numbers. They’ve also chosen not to indicate which month or week their units were built.

Included brandsExamples of serial numbers
NavienExample one: ****C14X******* (production year is 2014)

Example two: ****-2005-****-**** (production year is 2005)

Rinnai

Rinnai products carry two serial number patterns (5). On their newer models, they use letters to indicate both the month and year.

For their older water heaters, pre-2010, Rinnai used numerical references. The first two for the year and the following two refer to the month.

Their current system starts from the year 2009, and is as follows:

Year (1st letter)Month (2nd letter)
A = 2009

B = 2010

C = 2011

D = 2012

E = 2013

F = 2014

G = 2015

H = 2016

J = 2017

K = 2018

L = 2019

M = 2020

N = 2021

P = 2022

R = 2023

S = 2024

T = 2025

W = 2026

X = 2027

Y = 2028

Z = 2029

A = January

B = February

C = March

D = April

E = May

F = June

G = July

H = August

J = September

K = October

L = November

M = December

Included brandsExample of serial numbers
RinnaiExample one: JB. **-****** (February 2017)

Example two: 04.03-****** (March 2004)

When Should You Replace Your Water Heater?

A water heater made from durable material and regularly maintained should last many years. However, no matter how good your water heater is, it won’t last forever.

Here are a few signs to watch for that could indicate your water heater is running out of steam.

1. Age of Your Unit

The first question to ask yourself is “How old is the water heater?” The general lifespan could be in the region of 10 to 15 years. Using this guide should help you determine your water heater’s age.

Most experts, however, will likely suggest replacing your unit by the time it reaches its 15th birthday. Even if it’s still working efficiently, its performance may soon begin to drop due to its age.

2. Less Hot Water

If you suddenly begin to notice a decline in the volume of hot water, it might be time to consider a replacement.

Most people begin to notice a lack of water temperature — instead of hot water, it may flow lukewarm. Or perhaps the water heater suddenly struggles to provide enough heat for an average eight-minute hot shower.

3. Higher Heating Bills

A considerable amount of household energy is spent on heating water — 18 percent (6). When an old water heater begins to reduce in performance, so does its efficiency. As a result, you may notice your utility bills rising.

4. Corrosion

Noticing corrosion on your water heater is a sure sign it’s time for a replacement. This shouldn’t, and rarely does, appear until the unit is significantly old.

One sure way of spotting this is when you see red discoloration in the water. Red tinted water may mean rust inside the water heater.

You Might Also Like
Man opening the lid of a water heater to check for problems7 Common Water Heater Problems (& How to Fix Them)

Age Is Not Just a Number

Water heaters don’t last forever — on average, most will need to be replaced within 10 to 15 years of service. However, unless you’re keeping track of its birthdays, you’ll have to determine your water heater’s age for yourself.

Fortunately, this is fairly easy as long as you know the serial number and brand name — and you have a handy guide to help you decode it.

Do you know how old your water heater is? We’d like to see your answer in the comments below, as well as any other questions you may have.

Was this article helpful?

👍
👎
×

What went wrong?

This article contains incorrect information

This article does not have the information I am looking for

There is a problem with the website

×

How can we improve it?

All feedback is anonymous. If you would like a reply, please email us instead.

×

We appreciate your feedback!

We will look into this issue as soon as possible.

×

Thank you for your feedback!

Please share this article with someone you care about and leave a comment below.

Share this article:

Headshot of peter

About the Author

Peter Gray

Peter has been a homeowner for 35+ years and has always done his own repair and improvement tasks. As a retired plumber, Peter now spends his time teaching others how they can fix leaks, replace faucets, and make home improvements on a budget.
It’s Here! Our List of the Best 50 Gallon Water HeatersBest 50 Gallon Water Heaters of 2020
Air in Hot Water Line: Common Causes and the Best Ways to Fix ItHow to Fix Air in Hot Water Lines
AO Smith Tankless Error Code TroubleshootingAO Smith Tankless Error Code Troubleshooting
A.O. Smith Water Heater Reviews (2020 Guide)A.O. Smith Water Heater Reviews (2020 Guide)
Bradford White Tankless Error Code TroubleshootingBradford White Tankless Error Code Troubleshooting
Bradford White Water Heater Reviews: Everything You Need to KnowBest Bradford White Water Heaters Reviews of 2020

Leave a Comment