How old is my American water heater?

By Dana Whitlock. Updated October 2026. Widely documented.

On an American tank, a serial starting 0124 does not mean January 2024. It means the 24th week of 2001. Read the first four digits as year, then week, and 9950123040 becomes week 50 of 1999, mid-December. The layout has held since at least the late 1980s.

We rate this one Widely documented. American Water Heater does not post a decoder of its own, but a 2001 federal recall and a 2019 notice from its parent company describe the same year-week layout, and home inspector charts agree.

Where to find the label on a American water heater

The data plate is on the front of the heater, where the 2001 recall notice told owners to look. A.O. Smith's recall paperwork for this family places it next to the gas control valve or thermostat. Light it with a flashlight from the side if the print is shiny. Read it without opening anything. The thermostat covers on an electric tank guard live connections, and the gas control is not something to touch.

How to read the code

Split the serial after the fourth digit. Digits one and two are the year, two-digit style, so 89 is 1989 and 13 is 2013. Digits three and four are the production week, from 01 to 53. The rest is a running count; on newer units it may include a plant letter in the A.O. Smith style. Older American serials are often ten digits with no letters at all. To turn a week into a month, divide by four and a bit: week 06 is early February, week 24 is mid-June, week 45 is early November.

Real serials in this code

When the format changed

The year-week layout has been stable for decades, so the main risk is misreading it as month and year, the way Rheem serials work. A recall in 2001 makes the difference plain: affected tanks had serials starting 0124 through 0127 and were sold from June to September 2001, which fits week 24 to 27 of 2001 and does not fit any month reading. If a decode gives you a year far in the future or a tank that would be 80 years old, you have flipped the digits. One more caution: American Appliance Manufacturing of Santa Monica was a different company with different codes, so an old tank labeled 'American Appliance' needs a different approach.

Who makes American

American Water Heater is now one of A.O. Smith's brands. The same plants turn out U.S. Craftmaster tanks and Whirlpool-branded tanks, and all three read the same way. Older American-built names in a 2001 recall included Proline, Envirotemp, Mor-Flo, Powerflex and Premier Plus. A.O. Smith's own brands adopted a matching year-week code around 2008, and a 2019 recall covering American, A.O. Smith, State, Reliance, U.S. Craftmaster and Whirlpool tanks identified them all by first four digits between 1115 and 1631.

How sure is this?

Widely documented. American doesn't publish this code; it comes from recall notices, service literature and inspector references. We tested the american water heater rules against 6 serials, 4 of them with a date known from a recall notice, a printed label date or the maker. None decoded to a wrong year; codes whose year mark repeats show every possible reading. Always confirm with American's serial lookup before you spend money on the answer.

Quick notes

• Year first, week second. If you get a month above 12, you are reading it the right way.
• Mor-Flo, Envirotemp and Proline labels are American-built and decode the same way.
• Check American's warranty verification page with the full serial before paying for a repair on a tank near the end of its warranty.
• DOE's analysis puts the average electric tank at about 15.1 years and gas at about 14.5, so an American tank from the early 2010s is in the zone where replacement quotes are worth having.