How old is my water heater?
The build date is coded into the serial number on the rating plate, the large label on the side of the tank. Every manufacturer codes it differently, so choose the brand and type the serial.
Find the age from the serial number
Choose the brand for its date-code chart
- A. O. Smith3 serial formats
- American1 serial format
- Bradford White2 serial formats
- GE2 serial formats
- Kenmore2 serial formats
- Navien2 serial formats
- Reliance3 serial formats
- Rheem2 serial formats
- Richmond2 serial formats
- Rinnai2 serial formats
- Ruud2 serial formats
- State3 serial formats
- Whirlpool1 serial format
Where is the serial number?
On a tank water heater the rating plate is a large paper or foil label on the side of the jacket, usually at chest height above the gas control or the upper element cover. It lists the model number, the serial number, the tank capacity in gallons and the input rating.
On a tankless unit the label is on the side or the underside of the case. On some models it is inside the front cover.
The brand on the jacket is not always the company that built the tank. Store brands and several well-known names are built by one of a few manufacturers, and the serial follows the builder’s format.
No readable serial number?
- Some rating plates print the manufacture date in plain text, labelled “MFG date” or “Date of manufacture”. When it is there, use it. The serial is only needed when no date is printed.
- A safety-standard number followed by a year, such as “ANSI Z21.10.1” and a year, is the edition of the standard the heater was certified to. It is not the build date. The heater is at least as new as that year.
- An installer’s sticker or a plumbing permit gives the installation date. Tanks are normally installed within a year of manufacture.
- The manufacturer’s support line can read the date from the model and serial numbers.
What the age means
| Equipment | Typical service life |
|---|---|
| Tank water heater | 10 to 15 years |
| Tankless water heater | about 20 years |
Questions and answers
How long does this equipment last?
Typical service life: tank water heater 10 to 15 years and tankless water heater about 20 years. Water quality, maintenance and how hard the equipment works move a given unit above or below the range.
Does the serial number show the tank size?
No. The serial number carries the date and a production sequence. The capacity in gallons is printed on the rating plate and is also part of the model number.
Is the installation date the same as the manufacture date?
No. The serial number gives the date the heater was built. It was installed later, normally within a year. When there is no proof of the installation date, manufacturers generally count the warranty from the manufacture date.
Other equipment
- How old is my furnace?Gas, oil and electric furnaces
- How old is my AC unit or heat pump?Central air conditioners and heat pumps
- How old is my refrigerator?Refrigerators and freezers
- How old is my appliance?Washers, dryers, dishwashers, ranges
Page last reviewed on October 5, 2026. Method and sources.