How old is the water heater, and how long does it have
Updated October 2026
Find the label
Every water heater has a rating label on the side of the tank, usually at about eye level. It lists the model, the gallons, and a serial number. The date the heater was made is inside the serial number. The format depends on who built it.
Rheem and Ruud
The serial number starts with four digits: the month, then the year. A serial beginning 1209 was made in December 2009. One beginning 0316 was made in March 2016.
A. O. Smith and State
On these the first two digits are the year and the next two are the week of that year. A serial beginning 1437 was made in the 37th week of 2014, which is September. The company does not publish the format itself, so if the result makes no sense, call the number on the label and read them the serial.
Bradford White
Bradford White uses letters. The first letter is the year and the second is the month.
| Letter | Year | Letter | Year |
|---|---|---|---|
| A | 2004 | L | 2014 |
| B | 2005 | M | 2015 |
| C | 2006 | N | 2016 |
| D | 2007 | P | 2017 |
| E | 2008 | S | 2018 |
| F | 2009 | T | 2019 |
| G | 2010 | W | 2020 |
| H | 2011 | X | 2021 |
| J | 2012 | Y | 2022 |
| K | 2013 | Z | 2023 |
The letters repeat every 20 years, so A is also 1984. A tank that looks its age is the older one.
The month letters run A for January through M for December, skipping I. So a serial beginning KC was made in March 2013.
How long they last
The manufacturers put the service life of a tank water heater at 8 to 12 years. The U.S. Department of Energy says 10 to 15. Tankless units are rated at 15 to 20.
Warranties are shorter than that. Tanks are sold with 6, 9 or 12 year coverage depending on the model.
What shortens it
Sediment. Minerals in the water settle on the bottom of the tank and build up. Rheem recommends flushing a tank once a year, and every six months where the water is hard.
Water on the South Shore is not all the same. Quincy and Milton are supplied by the MWRA, whose water is soft, about 16 milligrams per liter. Towns with their own supplies, such as Weymouth and Braintree, publish their own figures in the annual water quality report.
What to do with the number
Under eight years old and not leaking from the tank: a repair is usually worth pricing.
Past twelve, or leaking from the tank at any age: it is time for a new one. What that costs here.
In between, compare the repair price to what a new tank costs before agreeing to either.