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Water heater age by brand: what the serial number tells you.
A brand-by-brand look at which makers publish a date code, with decoders for the two that do and official links for the rest.
Only some water heater makers publish how to read the date from a serial number. This guide lists what each maker's own website said when it was read on 2026-11-01: the two with a published date code (Bradford White and Rheem, which have decoders on this site) and the ones where no date table was found, with a link to the page that does exist for that maker, usually warranty lookup or registration. If a brand is not listed, no maker page was read for it, and nothing here should be taken as a statement about it.
What each maker publishes
| Brand | Date code published? | What the maker says |
|---|---|---|
| Bradford White | Yes | The first two characters give the year and month, as letters. See the Bradford White decoder. |
| Rheem | Yes | Ten characters; the first four digits are month then year. See the Rheem decoder. |
| A. O. Smith | Not found | The support page offers a warranty status check that takes the serial number, and product registration through a QR code on the rating plate. No date table on the pages read. |
| State Water Heaters | Not found | Same pattern as A. O. Smith on its support page: warranty status check, registration and QR code on the rating plate. No date table found. |
| American Water Heater | Not found | Support page with warranty status check and registration. No date table found. |
| Reliance | Not found | Support page with warranty status check, registration and a QR code on the rating plate. No date table found. |
| Navien | Not found | The tankless FAQ points to a document showing where to find the serial number and says registration needs the serial number, installation date and owner and installer details. No date scheme found. |
| Noritz | Not found | The warranty registration form asks for the model and serial number as they appear on the heater. No date scheme found. |
| Rinnai | Not found | The support page directs owners to product registration within 90 days. No date scheme found on the pages read. |
| Lochinvar, Whirlpool, Kenmore, Bosch, Westinghouse, Vaughn | Not covered | No maker page with a date code was found that could be read, so nothing is stated for these. |
"Not found" means the support, FAQ and registration pages listed in the sources did not contain a date code. It does not mean the maker has no scheme, only that this site will not guess at one. Guessing from forum posts is how people end up believing a tank is ten years younger than it is.
How to find the real age when there is no published code
- Photograph the rating plate. Make sure the model number, serial number and any QR code are readable. Bradford White and Rheem both show the rating plate as the place to look.
- Use the maker's warranty check. Several makers, including A. O. Smith, State, American and Reliance, offer a warranty status check that takes the serial number. The answer comes from the maker's own records.
- Check the paperwork. A permit, an invoice or the original warranty card gives an installation date, which is what matters for most warranties.
- Call the maker. Technical support can read a date from the serial against their own records.
What age means in practice
Reliance says the life expectancy of a water heater is about 8 to 12 years, varying with location, design, quality of installation, maintenance and water quality, and that a unit over 10 years old that leaks around the base or runs erratically is probably due for replacement. That is one maker's guidance, not a guarantee. A tank that is old, wet around the base or noisy is a reason to get a plumber to look at it, whatever its age.
When you replace a unit, the tank water heater size calculator and the tankless GPM calculator help with sizing, and the recovery time calculator shows how fast a given tank reheats.
FAQ
Can I tell how old my water heater is from the serial number?
Sometimes. Bradford White and Rheem publish how to read the date from the serial number. For other makers this guide found no published date code, so use the maker's warranty check or the installation paperwork.
Do all water heater brands use the same date code?
No. Bradford White uses a year letter and a month letter. Rheem uses month and year digits. The other makers read for this guide did not publish a code on the pages checked.
Where is the serial number on a water heater?
On the rating plate on the tank or cabinet. Bradford White and Rheem both point to the rating plate; some A. O. Smith family labels also carry a QR code that opens registration.
Is the manufacture date the same as the warranty start?
No. Warranties usually run from installation or registration, and a unit can be built months before it is installed. Check the maker's warranty terms.
Why not decode the other brands too?
Because no maker page with a date table was read for them. A guessed decoder can give a wrong age, so this site only decodes schemes the maker publishes.
How long does a water heater last?
Reliance gives about 8 to 12 years on its replacement guide, depending on location, design, installation, maintenance and water quality. Other makers and unit types vary.
Sources
Each page was opened and read on 2026-11-01. Manufacturers can change these pages without notice.
- Bradford White: My water heater: year and month letter tables and rating plate guide.
- Rheem: How to locate and read your Rheem water heating serial numbers: ten-character layout, month and year digits.
- A. O. Smith support: warranty status check, product registration and QR code on the rating plate; no date table found.
- State Water Heaters support: same support layout; no date table found.
- American Water Heater support: warranty check and registration; no date table found.
- Reliance support: warranty check, registration and QR code; no date table found.
- Reliance: when to repair or replace: the 8 to 12 year life expectancy statement.
- Navien tankless FAQs: serial number location and registration requirements.
- Noritz warranty registration: registration asks for model and serial number.
- Rinnai support: registration within 90 days.
General information only
This page is general information, not professional plumbing, safety or warranty advice. A serial number shows when a unit was made, not when it was installed or whether a warranty still applies. Confirm warranty status with the manufacturer and have a licensed plumber assess any unit you are unsure about.