To find your water heater's age, read the serial number on the rating label on the side of the tank. Rheem's first four digits are the month and year it was built, and Bradford White's first two letters are the year and month. To check warranty status, enter that serial in the maker's online lookup.
Where is the serial number?
Look for the rating label on the side of the tank. That's where the model and serial numbers are printed. On a tank in a tight closet or garage corner, you may need a flashlight and a phone camera to read it. A clear photo of the whole label is worth taking anyway, because you'll need both the model and serial numbers for any warranty call.
Rheem says the serial number identification on all Rheem water heating product rating labels contains ten digits. Bradford White's serial starts with two letters. Other brands use their own formats, so match the code to your brand before you decode it.
How do I read the date in the serial number?
Each maker encodes the date differently. Here are two published keys.
### Rheem
Rheem's example serial is 1209D01234. It breaks down like this:
| Characters | Example | Meaning |
|---|---|---|
| 1st and 2nd | 12 | Month made (December) |
| 3rd and 4th | 09 | Year made (2009) |
| 5th | D | Plant line code |
| Last five | 01234 | Consecutive serial number |
So that heater was built in December 2009. Read the first four digits of yours the same way: month first, then year.
### Bradford White
Bradford White says "The first two characters of the serial number represent the year and month of manufacture." The first letter is the year and the second is the month.
For the month, Bradford White uses A through M and skips I:
| Letter | Month | Letter | Month |
|---|---|---|---|
| A | January | G | July |
| B | February | H | August |
| C | March | J | September |
| D | April | K | October |
| E | May | L | November |
| F | June | M | December |
For the year, each letter stands for two possible years, 20 years apart. The chart lists A as 1984 or 2004, and also as 2024. D is 1987 or 2007, K is 1993 or 2013, and Z is 2003 or 2023. Bradford White skips the letters I, O, Q, R, U and V in the year column.
Bradford White gives one clue for picking between the two years. The rest of the serial is a sequential production number, "seven digits in length before December 2007 (DM), and eight digits in length after." Count the digits after the two letters. Eight digits means the heater was built in December 2007 or later. Seven means it was built before then. The home's records and the tank's condition help settle the rest.
### Other brands
A. O. Smith's registration page asks you to "Have your serial # or reference # ready to check status." It doesn't publish a decoding chart on that page, so the simplest path for that brand is its own warranty lookup. For a broader look at dating the rest of your plumbing, see how to tell the age and condition of home plumbing.
How do I check whether it's still under warranty?
Use the maker's lookup, and have your serial number ready.
- Rheem says that to verify whether your water heater is still under warranty, you can use its water heater verification tool, which will require your serial number.
- A. O. Smith offers a warranty status check on its registration page, using the serial or reference number.
- Bradford White's warranty says to "Please have model number and serial number ready" when you contact its warranty group.
While you're looking it up, check your model against recalls too. See how to check a water heater for a recall.
### When does coverage start?
Usually on the day the heater was installed, not the day it was built. But if you can't prove the install date, the maker falls back on the build date in the serial:
- Rheem's warranty policy says its residential coverage periods begin on the date the heater was installed. If no proof of the install date is provided, Rheem "will use the water heater's date of manufacture plus ninety (90) days."
- Bradford White's limited warranty "runs from date of installation (or without proof of installation, from three (3) months after the date of manufacture)."
That's why the install invoice is worth keeping. A heater that sat in a warehouse for months before it went in may have more coverage left than the serial alone suggests.
### Keep the label and the paperwork
The rating label isn't just for reading. Both makers want it back if a tank fails under warranty. Rheem says that at a minimum it requires the return of the original rating label removed from each defective water heater before providing a warranty allowance. For a tank replacement claim, it adds that photocopies of the label are not acceptable. Bradford White's warranty says it won't replace a water heater without prior receipt of the actual rating plate and a copy of the original sales receipt.
So don't peel, paint over or cover the label. Keep the install invoice and sales receipt with your home records, and the FTC suggests you save a copy of the warranty itself. Bradford White's warranty also has a spot to fill in the model and serial numbers for your reference.
What can limit or void coverage?
Warranties have conditions, and they're worth reading before you need them. The Federal Trade Commission notes that sometimes "you'll have to return a product registration card first to qualify for warranty service." It also says that if parts or repairs aren't listed as covered, you should assume they aren't.
Here's what the two manufacturer documents above spell out:
- Registration. Bradford White's warranty says "The Warranty Registration card must be returned in order to activate warranty coverage."
- Original owner and location. Bradford White's coverage applies only to the original consumer purchaser while the heater stays installed at its original place of installation.
- Installation. Bradford White excludes installations made in violation of state or local plumbing codes, or contrary to the written instructions.
- Sediment. Bradford White lists "sediment or lime precipitate in the tank" among the adverse local conditions it doesn't cover.
- Timing. Rheem reserves the right to deny any claim submitted more than 90 days after the in-warranty defect occurred.
- Paperwork. Rheem requires a copy of the contractor's invoice for labor claims, showing the model number, serial number and location of the heater.
Terms vary by model and change over time, so read the warranty that came with your heater rather than assuming these apply word for word.
### Why the sediment clause matters in Phoenix
Phoenix's 2025 water quality report lists hardness of 10 to 17.6 grains per gallon, and says "Hard water can cause some types of scaling in pipes and water heaters." For how to keep that buildup down, see how often to flush a water heater in Phoenix.
What if the heater is out of warranty?
Age alone doesn't mean it's time to replace it. A well-kept tank past its warranty can still have life in it, and a younger one that's leaking from the tank may not. Our guide on whether to repair or replace a water heater walks through that call.
If you'd like a second set of eyes on the label, the tank or the warranty paperwork, call HQ. We're available 24/7, licensed and insured, and every estimate is free with upfront pricing.