ToftThis covers Rheem, Ruud, Richmond, GE, General Electric, Hotpoint, Vanguard, Western Auto, Montgomery Ward, Citation, Cimarron, Coast to Coast, Energy Master, Mainstream, ABS, Lowe's. The serial number is on the rating label on the side of the tank. Some labels also print the manufacture date.
Ten characters: four digits, a letter, then five digits. Some labels put one to four letters in front; skip them. The first two digits are the month and the next two are the year.
Example: 1209D01234 was made in December 2009.
Newer tanks: a letter, then nine digits. The first two digits after the letter are the week of the year, and the next two are the year.
Example: A141511869 was made in week 14 of 2015.
This is the date the unit was made. It was usually installed soon after, but it can be later. If a serial doesn’t fit any of these patterns, look on the label for a printed manufacture date.
Checked in October 2026.
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