What TankBirthday Does
Every water heater has its manufacture date encoded in the serial number on the rating plate — but every manufacturer encodes it differently, and none of them explain it on the plate itself. TankBirthday exists to close that gap. Type a serial number into one of our free decoders and you get the manufacture date back: the month and year, or at minimum the honest range of possible years.
The site covers the three major tank manufacturers — Rheem, A.O. Smith, and Bradford White — the three major tankless brands (Navien, Rinnai, and Bosch), and fifteen store-brand labels like Kenmore, Whirlpool, State, and Reliance that are really rebadged units from those same factories. The water heater age chart lines every format up side by side if you'd rather match the pattern yourself.
Who Maintains It
TankBirthday is built and maintained by an independent developer — the same person behind owningafender.com, a guitar serial-number and tech-resource site that uses the same decoder methodology. The approach transfers directly: take a serial number format the manufacturer never bothered to document clearly, verify it against every public source available, encode it in software, and be upfront about the cases that can't be resolved. There is no plumbing company, manufacturer, or retailer behind this site, and nothing here is for sale.
How the Decoders Are Verified
Every serial format on this site is checked against public manufacturer documentation, the InterNACHI water heater dating chart, and the Building Intelligence Center before it is encoded. Where sources disagree, the decoder follows the manufacturer's own published guidance first.
Just as important is what the decoders refuse to do. They are deliberately conservative: when a serial number is ambiguous, the decoder says so instead of guessing. Bradford White is the clearest example — its year letters repeat on a 20-year cycle, so the letter F means 1989 or 2009 with no character in the serial to separate them. Rather than picking one, our decoder lists every plausible year and explains how to narrow it down using the unit's condition, the ANSI revision year on the rating plate, and the age of the house. A tool that confidently guesses wrong is worse than one that admits the limits of the format.
A Necessary Disclaimer
TankBirthday is a reference tool, not professional plumbing advice. Decoded dates are as reliable as the serial number you type in and the format documentation behind it — always confirm against the rating plate, which sometimes prints the manufacture date in plain text. For installation, repair, warranty claims, or safety questions like gas connections and venting, consult a licensed plumber or the manufacturer directly.
Sources
- InterNACHI water heater dating chart — the industry-standard cross-brand reference for serial formats.
- Building Intelligence Center — water heater age guides covering dozens of brands, current and defunct.
- Manufacturer documentation from Rheem, A.O. Smith, Bradford White, Navien, Rinnai, and Bosch, linked on each brand's decoder page.