Pick the brand, type the serial number from the label and see the year it was built, its age and where it sits against a typical water heater life.
The brand comes first because the same digits mean different things on different labels.
Bradford White uses two letters. The first is the year, on a 20-year cycle, and the second is the month. Rheem, Ruud and Richmond print the month and then the year in the first four digits after any letters. A.O. Smith, State, American and the store brands they build print the year and then the week.
The tool also reads Rinnai, Navien, Noritz, Takagi and Bosch tankless serials, and it tries each published layout for the brand you pick.
A storage tank is steel with a glass lining and a sacrificial anode rod. Once the rod is used up, the water goes after the steel and the tank fails from the inside out. A conventional tank typically lasts 6 to 12 years and a tankless unit 10 to 20 years with regular descaling. Past ten years, a tank that sits above finished space deserves a closer look.
Bradford White reuses its year letters every 20 years, so D means 1987 or 2007 and M means 1995 or 2015. The tool lists both and asks which decade the heater was installed. Two tiebreakers help. An 8-digit sequence after the letters means late 2007 or newer, and the ANSI standard year on the label is the earliest the unit could have been built.
The status compares the age to the typical life for a tank or a tankless unit. Early in its life and mid-life mean no action is needed beyond normal maintenance. In the replacement window means a larger repair deserves a second opinion. Past typical life means it is worth planning ahead. The list of questions at the bottom of the result is for the plumber at your next visit.
On a sticker or metal plate on the side of the tank, usually near the gas control or the electrical access cover. Tankless units carry it on the side or bottom of the case or inside the front cover. The same label lists the model number and, on newer units, the manufacture date.
The first letter is the year and the second is the month. DG6322957 reads D for 2007 (or 1987) and G for July. Year letters skip I, O, Q, R, U and V, and month letters run A to M skipping I.
After any letter prefix, the first two digits are the month and the next two the year. 0804B10488 was built in August 2004 and RHLN0106534307 in January 2006. Newer styles put the week first, and the tool tries each published layout in turn.
A conventional storage tank typically lasts 6 to 12 years and a tankless unit 10 to 20 years with regular maintenance. Hard water, an anode rod that was never replaced and a tank that was never flushed pull the number down.
At 12 years a tank is at the top of its typical range. If it sits above finished space, shows rust at the bottom seam or the fittings, or the anode rod was never replaced, planning the replacement is easier than reacting to a leak. Ask a plumber to check the anode, the seams and the relief valve.
Data: manufacturer serial number formats from public technical references, compiled 2026-09, and typical service lives from the InterNACHI life-expectancy chart.
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