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How old is my Rheem and Ruud water heater?
Skip any letters at the start of a Rheem or Ruud serial number. The next four digits are the date: the first two are the month and the next two the year. 0612… is June 2012.
Reading the code
1Q101608457: Letters, then month and year: October 2016.
2RHLN 0106534307: However many letters come first: January 2006.
3RHUN M181401735: On some lines the first two digits are the week, not the month: 18 can't be a month, so it's week 18 of 2014. The year is still the 3rd and 4th digits.
405.05-000021: An older style with a dot: year first, then month. May 2005.
Ruud water heaters are made by Rheem and use the same codes.
Where the serial number is
On the rating label on the side of the tank, usually near the top, marked "Serial No." or "S/N".
How long they last
Most tank heaters last 8 to 12 years. Warning signs: rusty hot water, rumbling, water at the base. What a replacement costs, and the permit.
Other makers
Bradford White · A.O. Smith and State · Any brand, from a photo