Find Your Intertherm Water Heater's Age
The fastest way to date an Intertherm water heater is the serial number on its rating plate. Intertherm is a Nordyne / Nortek Global HVAC brand aimed at manufactured and mobile homes, and its water heaters were built by major tank manufacturers — most following Rheem's serial date coding. Enter your serial number in the free decoder above, or read on to decode it by hand.
Where to Find the Serial Number
Look for the rating plate (also called the data plate) — a silver or white sticker on the side of the tank, usually in the upper half. On manufactured-home models it may sit near the top or beside the side inlet/outlet connections. It shows the model number, serial number, capacity, and input rating, and some units print the manufacture date in plain text next to the serial — if yours does, use that date directly.
How the Intertherm Serial Format Works
Modern format (month + year). Ignore the letter prefix — Intertherm serials may start with RN, R, and similar factory prefixes, just like Rheem. The first four digits after the prefix are the date: two digits for the month, then two for the year.
Worked example — RN0197147899:
- Prefix:
RN(ignore) 01= January (month)97= 1997 (year)- Result: manufactured January 1997
Week + year variants. Some serials encode the week of the year instead of the month: the first two digits are the week (01–52), the next two are the year.
One caveat. A minority of Intertherm water heaters were produced by State Industries (now part of A. O. Smith) and may follow State's coding instead. If the decoder above rejects your serial, try our A. O. Smith or State lookup before giving up.
Why the Age of Your Intertherm Water Heater Matters
- Lifespan. Tank-style water heaters typically last 8–12 years. Past that window, the risk of tank corrosion and leaks climbs sharply — and a failed tank can release dozens of gallons of water into your home.
- Warranty. Tank warranties commonly run 6, 9, or 12 years from the manufacture date (not the install date). The serial number tells you whether you're still covered before you pay for a repair.
- Replacement planning. Knowing the exact age lets you replace on your schedule — comparing quotes and choosing a model — instead of making an emergency decision after a failure.
Sources
Serial format details verified against the Building Intelligence Center's Intertherm water heater age guide, InspectApedia's Intertherm water heater age decoder, Rheem's official serial number guide, and the InterNACHI water heater dating chart.