Find Your Ruud Water Heater's Age
The fastest way to date a Ruud water heater is the serial number on its rating plate. Enter it in the free decoder above and you'll get the manufacture date in seconds — or read on to decode it by hand.
Who Makes Ruud Water Heaters?
Ruud is a Rheem Manufacturing Company brand. Rheem acquired Ruud decades ago, and today Ruud water heaters are built in the same factories as Rheem and Richmond units. Because of that shared production, Ruud serial numbers use exactly the same date-code format as Rheem — the decoder above works identically for both brands.
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 tank models. It shows the model number, serial number, capacity, and input rating, and on many newer Ruud units it prints the manufacture date in plain text.
On Ruud tankless units, the plate is typically on the side of the case or behind the front cover. If the sticker is dirty or faded, take a photo and increase the contrast — even a partial serial is often enough.
How the Ruud Serial Format Works
Modern format (month + year). Ignore the letter prefix — Ruud serials may start with RU, R, RN, RH, RHNG, and similar factory prefixes. The first four digits after the prefix are the date: two digits for the month, then two for the year.
Worked example — RU 0904B21710:
- Prefix:
RU(ignore) 09= September (month)04= 2004 (year)- Result: manufactured September 2004
Older format (week + year). Some older Ruud 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. Tankless units often use a format like 05.19-000021, where the digits before the dash are month and year (May 2019).
Why the Age of Your 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. Ruud 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 instead of making an emergency decision after a failure.
- Buying or selling a home. Inspectors routinely report water heater age, and a unit near the end of its life often becomes a negotiation point.
Sources
Serial format details verified against the InterNACHI water heater dating chart, Rheem's official guide to reading serial numbers, Ruud's own water heater age tool, and the Building Intelligence Center's Ruud water heater age guide.