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How old is my Reliance water heater?

Type the serial number from the Reliance label to see when it was built. Reliance units are built by A.O. Smith, so the serials follow that company's format.

Scan insteadWhere is the label?

Example

1211A018632
  • 12Year: 12 = 2012
  • 11Week: 11 (around March)

Built Week 11 of 2012 (around March)

14 years, 7 months old

Past typical life. Past the usual 6 to 12 year lifespan. Watch for rust-colored hot water, rumbling or popping from the tank, and moisture around the base.

Plan the replacement

  • Plan the replacement before it fails. A failed tank can release its full contents onto the floor.
  • Check the base and the fittings on top for moisture or rust now, and keep checking.
  • Know where the cold water shutoff above the tank is, so you can stop a leak quickly.
  • Some home insurers ask the age of the water heater, and in Florida a 4-point inspection flags tanks over 10 years. Check before you renew or buy a house.
  • Tank warranties usually run 6 to 12 years. Coverage usually counts from the install date or from a few months after the build date, so the build date is a good guide.
How this was read
  1. The first two digits, 12, are the year: 2012.
  2. The next two digits, 11, are the week of the year, so about March.

Format: Year and week. Sources: CPSC 2019 A.O. Smith recall (year and week), CPSC 2008 A.O. Smith and State recall (month letters), A.O. Smith Service and Warranty Guide (PDF).

Reading a Reliance serial number

Reliance is an A.O. Smith brand sold through hardware stores. Its serials use the A.O. Smith formats.

About Reliance

  • Reliance Water Heater Company was founded in 1981 to supply hardware and home improvement retailers.
  • Reliance series numbers match the tank warranty. In the 2007 catalog the 606 Series had a 6-year warranty, the 909 Series 9 years and the Sta-Kleen 1212 Series 12 years.
  • Reliance’s 2007 catalog lists its address as 500 Tennessee Waltz Parkway in Ashland City, Tennessee, home of State Water Heaters.

Sources: Reliance: The Brand Created for You and Your Customers (Reliance catalog, 2007), About Us | State Water Heaters

Year and week

Used about 2008 to today. Example: 1719106145074

The first two digits are the year and the next two are the week of the year. A letter may come first or in the fifth position; it is a plant code. A CPSC recall notice confirms this reading: "the first four digits represent the year and week of production".

Worked example: 1211A018632 was built Week 11 of 2012 (around March), so it is 14 years, 7 months old as of October 2026.

Sources: CPSC 2019 A.O. Smith recall (year and week), CPSC 2008 A.O. Smith and State recall (month letters), A.O. Smith Service and Warranty Guide (PDF)

Plant letter, month letter and year

Used through June 2004. Example: MK890054977H43

The first letter is the factory, the second letter is the month (A is January, I is skipped), and the next two digits are the year. MK89 means October 1989.

Worked example: MK89-0054977-H43 was built October 1989, so it is 37 years old as of October 2026.

The full lookup tables are on the A.O. Smith page, since Reliance uses the same code.

Sources: CPSC 2019 A.O. Smith recall (year and week), CPSC 2008 A.O. Smith and State recall (month letters), A.O. Smith Service and Warranty Guide (PDF)

Month letter and year

Used july 2004 to about 2008, and older State units. Example: L07A071460

The first letter is the month (A is January, I is skipped) and the next two digits are the year. L07 means November 2007.

Worked example: L07A071460 was built November 2007, so it is 18 years, 11 months old as of October 2026.

The full lookup tables are on the A.O. Smith page, since Reliance uses the same code.

Sources: CPSC 2019 A.O. Smith recall (year and week), CPSC 2008 A.O. Smith and State recall (month letters), A.O. Smith Service and Warranty Guide (PDF)

1970s series, month letter and year

Used 1970s to early 1980s. Example: 800M7209519

A three-character series code comes first, then the month letter and the year, like 800-M-72-09519 for December 1972.

Worked example: 800-M-72-09519 was built December 1972, so it is 53 years, 10 months old as of October 2026.

The full lookup tables are on the A.O. Smith page, since Reliance uses the same code.

Sources: CPSC 2019 A.O. Smith recall (year and week), CPSC 2008 A.O. Smith and State recall (month letters), A.O. Smith Service and Warranty Guide (PDF)

Reliance recalls

Recalls from the U.S. Consumer Product Safety Commission that name Reliance. Whether a unit is included depends on its model and build date; the checker above flags matches.

YearRecallHazard
2018A.O. Smith Ultra-Low NOx gas water heatersThe burner screen can tear and the burner can overheat a wood floor.
2005A.O. Smith 75-gallon propane water heatersSoot can build up on the burner and start a fire.
2004White-Rodgers controls on propane and convertible gas water heatersThe control can open slowly, so soot builds up on the burner and can start a fire.