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How old is my Ruud tankless water heater?

Serial number age decoder for Ruud tankless water heaters: 1 format era, the decode rule in plain English, transcribed tables, and the official lookup.

Serial number decoder for Ruud tankless water heater

Serial no.

Type the serial from the data plate, not the model number. Nothing is sent anywhere; the tables are in this page.

Format example: 0804B10488

Ruud tankless water heater serial numbers in the era not stated format encode the year as digits 3-4 (YY) and the month as digits 1-2 (MMYY prefix) (source: building-center.org).
Example: serial 0804B10488 decodes to August 2004.
Ruud's official lookup at rheem.registermyunit.com returns warranty terms.

Format eras

era not stated VERIFIED
####A#####digits 3-4 (YY)

How to read the serial

era not stated formatVERIFIED

Shape ####A##### · example 0804B10488 · confidence high

Year: digits 3-4 (YY)
Week or month: month = digits 1-2 (MMYY prefix)
Plant: letter at position 5

Example: serial 0804B10488 decodes to August 2004.

Trap: MMYY vs older 9-digit style (123451872: year = last 2 digits, week = 3rd-4th from last); also used on some older HVAC. Rheem's own site has no age page; only the warranty-verification tool.

Listed under Rheem in the source; Ruud is named in that format's family and the corporate link is an estimate, not a checked fact.

Where the data plate is on a tankless water heater

On the side or bottom of the wall-hung cabinet, or inside the front cover on the frame.

General guidance, not brand-specific: the owner's manual or the installer can point to the exact spot. See the data plate guide.

For scale only: the InterNACHI Standard Estimated Life Expectancy Chart for Homes lists Instant (on-demand) Water Heater at 10 years of expected service (nachi.org). That chart is a guideline, not a prediction for your unit.

Official lookup: the authority

Open the official Ruud lookup takes serial; returns warranty terms; URL unverified

This site is a reference built from published tables. The manufacturer's own lookup wins whenever the two disagree.

What we could not confirm

Ruud is treated as sharing Rheem's format because the source lists it in that family; the corporate relationship itself is an estimate.
Rheem acquired Ruud in 1959 (building-center). Ruud page lists the identical six Rheem HVAC styles (W291013412; CB5D302F099903346; 7351 M2806 16735; OR177 M2807 00097; 0804B10488 MMYY; 123451872) with the same chart images (Rheem-HVAC-style-1..6). ruud.com is (c) Rheem Manufacturing Company and ruud.com/warranties 404s; the lookup lives on Rheem's registermyunit portal (curl 200). Water-heater page: https://www.building-center.org/ruud-water-heater-age/ (not fetched this batch).