How old is my Whirlpool water heater?

Who actually made it

This is the part that decides everything else, so it comes first.

InspectApedia: "Whirlpool water heaters are manufactured under license by American Water Heater Company, Tennessee, and a limited warranty is provided by the manufacturer." Their brand index sends Whirlpool straight to the American Water Heater entry.

And American Water Heater is itself no longer independent. InspectApedia's company note on A.O. Smith: "By 2006 the company had purchased both Canadian GSW Incorporated and the American Water Heater Company."

So the chain is Whirlpool badge, American Water Heater build, A.O. Smith ownership. That is why the serial number follows the A.O. Smith convention and not a Whirlpool one. Fast Water Heater reaches the same place from the other direction, listing "American Water Heater, A.O. Smith, State, Reliance & Whirlpool" as one group sharing one system.

Reading the serial number

Take the first four digits from the line marked Serial No.

Fast Water Heater's worked example for this family: serial 1220 345678 is 12 for 2012 and 20 for the twentieth week, so mid-May 2012. InspectApedia's independent example for the same rule: 1604 123456 is week 4 of 2016.

Week to month, from Fast Water Heater, who call the conversion approximate:

If your serial starts with a letter, it is an older plate. Fast Water Heater: "Older American and State units sometimes use a letter for the month followed by a two-digit year." The letters run A for January to M for December with I left out. Applying that rule ourselves, a serial starting C04 is March 2004. That example is our own, worked from the rule above rather than quoted.

Why the maker matters more than the badge

Three practical consequences, and these are the reason this page exists rather than a line on a general decoder.

Warranty. InspectApedia is explicit that the limited warranty is provided by the manufacturer, not by Whirlpool. A warranty question therefore goes to the water heater business, not to Whirlpool's appliance support.

Parts. The tank, element, thermostat, dip tube and anode are American Water Heater parts. Our heating element and thermostat pages apply unchanged.

Decoding. If you look up "Whirlpool serial number" you will mostly find pages about washing machines and refrigerators, which use a completely different scheme. Those will give you a wrong answer on a water heater. This is the most common way people go astray here.

The mistake that costs years

Over seven years apart, and in the direction that makes an old tank look young. Fast Water Heater calls the month-first versus year-first confusion "the single most common mix-up we see".

Our note, marked as ours: that direction of error is the dangerous one. A 2012 tank mistaken for a 2019 tank reads as mid-life when it is actually past the usual 8 to 12 year failure window, and that is exactly the situation where people authorise a repair on a tank that is about to leak. The repair or replace page works that decision, and the lifetime cost page shows what the remaining years are actually worth.

Check it against the plate itself

Before you trust any decoded date, look at the rest of the rating plate. Many units print a manufacture or test date in plain text somewhere on the label, and that beats any decoding rule. The age decoder applies the rule above once you select Whirlpool, and sister brands are covered on the A.O. Smith and State pages.