About agebyserial.com
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Age by Serial turns the serial number on a water heater, furnace or air conditioner into a build date and an age. It is for people standing at a unit with its label: owners, buyers, landlords, inspectors and plumbers.
Independent of manufacturers
This site is not run by, endorsed by or affiliated with Bradford White, A.O. Smith, Carrier or any other manufacturer named on it. Brand names are used only to identify products. For warranty or technical questions, use the manufacturer.
How we source and check
Every decoder is built from a stated rule, and the rule is shown on the page next to the result. We rank sources in three tiers:
- Manufacturer sources are preferred: a manufacturer's own web page or manual.
- Government sources, such as a US Consumer Product Safety Commission recall notice, are used where the manufacturer does not publish a rule.
- Corroborating sources, such as inspector reference pages, may confirm an example but never supply a rule on their own.
Where a source leaves a gap, we say so on the page. For example, Bradford White's chart does not say how to choose between the two years a letter can mean; the tiebreak we use is our own derivation from a statement in its FAQ, and the page says that.
The never-guess rule
If a serial does not fit a rule we can check, the tool shows "Can't date this reliably" or "Brand not decoded yet" and no year. If two dates fit, it says the result is ambiguous and lists both. We would rather show nothing than a confident wrong year.
Lifespan ranges
The typical lifespan ranges on the remaining life calculator all come from a single source, InterNACHI's Standard Estimated Life Expectancy Chart. They are planning figures, not predictions for any one unit.
Data and credits
The decoders use published rules, not a downloaded dataset, so there is no third-party data file to credit. Each page lists the pages and manuals its rules come from.
Corrections
If a decode looks wrong, tell us through the contact page, with the brand, the serial and a photo of the label. We check it against the source and fix the page or the tool. The last-updated date on each page changes when its content or rules change.
Advertising
The site may carry advertising. Ads are labelled and kept away from the tools and results. See the privacy policy and terms of use.