Where to find the serial number
Look for the label on the side of the tank, usually near the top or near the controls. It lists the model number and the serial number. The serial number is usually marked "Serial No." or "S/N".
How each brand dates its heaters
| Brand | How to read it | Example |
|---|---|---|
| Rheem, Ruud | After any letters: 2 digits month, 2 digits year | 1209D01234 = Dec 2009 |
| A.O. Smith, State | 2 digits year, 2 digits week of the year | 2037… = Sept 2020 |
| Bradford White | 1st letter year, 2nd letter month | SF… = June 2018 |
Bradford White's year letters repeat every 20 years, so an "S" could be 2018 or 1998. The lookup shows the most recent possible year. If your heater looks much older than that, it's probably from 20 years earlier.
Older heaters sometimes use other formats. If the lookup can't read yours, a plumber can, or you can call the maker with the serial number.
What the age tells you
- Under 8 years: most tanks have years left. A problem is usually a part (a thermocouple, a valve, or an element), not the tank.
- 8 to 12 years: the usual time to replace it. Start setting money aside, and get a price now so you're not rushed later.
- Over 12 years: it's living on borrowed time. Check under it for rust or water now and then.
See what a new one costs with the water heater replacement cost calculator. If it's leaking right now, see what to do when a water heater leaks.
Questions people ask
How do I find out how old my water heater is?
Find the serial number on the label (the rating plate) on the side of the tank. The build date is coded into it. Rheem puts the month and year first, A.O. Smith puts the year and week first, and Bradford White uses two letters for the year and month.
How long does a water heater last?
HomeGuide puts tank water heaters at 8 to 12 years on average. Hard water and skipped flushing shorten that.
Should I replace a water heater just because it is old?
Not always. An old heater that is not leaking can keep going, but plan and budget for it so you are not forced into a rushed replacement when it fails. A tank leaking from the bottom needs replacing now.