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Rheem Water Heater Age by Serial Number — Free Lookup

Rheem

Enter the serial number from the rating plate (the silver data sticker on the upper side of the tank; on tankless units it is inside the cover on the right side). Works for Rheem, Ruud and Richmond — many Rheem plates also print the manufacture date directly as "MFG. DATE".

Find Your Rheem Water Heater's Age

The fastest way to date a Rheem water heater is the serial number on its rating plate. Rheem has used a few serial formats over the decades, but every one of them encodes the manufacture date in the digits right after any letter prefix — once you know where to look, it takes seconds. Enter your serial number in the free decoder above, or read on to decode it by hand.

This decoder also works for Ruud, Richmond, and other Rheem-made brands, which are built in the same factories and share the same date codes.

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 gas and electric tank models. It shows the model number, serial number, capacity, and input rating, and on many newer Rheem units it prints the manufacture date in plain text next to the serial.

On Rheem tankless units, the rating 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 to identify the format.

How the Rheem Serial Format Works

Modern format (month + year). Ignore the letter prefix — Rheem serials may start with R, RN, RH, RHLN, 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 — R 0819 B10488:

  • Prefix: R (ignore)
  • 08 = August (month)
  • 19 = 2019 (year)
  • Result: manufactured August 2019

Older format (week + year). Some older Rheem 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. For example, A141511869 decodes to week 14 of 2015 — early April 2015.

Tankless units. Rheem tankless serials often look like 05.19-000021, where the digits before the dash are month and year (May 2019 in this example).

If your serial doesn't fit any of these patterns, double-check the letters at the start and try again — or check the rating plate for a printed manufacture date, which overrides the serial.

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. Rheem tank warranties commonly run 6, 9, or 12 years from the manufacture date (not the install date), depending on the model. If your unit is leaking or underperforming, 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.
  • 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 and the Building Intelligence Center's Rheem water heater age guide.

Frequently asked questions

Where is the serial number on a Rheem water heater?
On the rating plate (data plate) — a sticker on the side of the tank, near the top on most models. It lists the model number, serial number, and often the manufacture date in plain text. Rheem tankless units carry the plate on the side or inside the front cover.
How do I read a Rheem water heater serial number?
On modern Rheem serials, ignore any letter prefix (R, RN, RHNG, etc.): the first two digits after it are the month and the next two are the year. For example, in R 0819 B10488, 08 = August and 19 = 2019. Many older serials use week + year instead, so a serial starting 1415 means week 14 of 2015.
Do Ruud and Richmond use the same serial format as Rheem?
Yes. Ruud and Richmond are Rheem sister brands made in the same factories, and their serial numbers follow the same date coding. You can decode them with the same tool.
My Rheem rating plate already shows a manufacture date. Do I still need to decode the serial?
No — if a plain-text manufacture date is printed on the rating plate, use that. The serial decoder is a fallback for plates where the date is missing, faded, or ambiguous.
How long does a Rheem water heater last?
Most tank-style gas and electric water heaters last about 8–12 years, depending on water quality, maintenance, and usage. If yours is past 10 years, start budgeting for replacement before it fails.
What is the warranty on a Rheem water heater?
Rheem tank warranties typically run 6–12 years depending on the model, with longer or lifetime tank coverage on premium lines like the Marathon. Terms are counted from the manufacture date — not the install date — so decoding the serial tells you whether a repair is still covered. Some models require registration for the full term; check the paperwork that came with the unit or the warranty guide on this site.