Rheem Water Heater Age: Serial Number Decoder
Rheem (and its sister brands Ruud and Richmond) put the build date in the first four digits of the serial number, after any letters: the first two are the month and the next two are the year. Many Rheem rating plates also print the manufacture date outright, which is the fastest, surest check.
How old is my Rheem water heater?
After any letters, the first four digits are the build date: the first two are the month and the next two are the year. Type your serial for an instant estimate, or read the printed “MFG. DATE” on the plate.
e.g. Where's my serial number?
Standard Rheem tank models use this code. Some specialty or non-standard units may use a different serial format.
Where to find your serial number
- On standard electric and gas tanks, the rating plate is usually on the side of the tank, often lower down near the bottom, with the model number, serial number, and frequently a printed MFG date.
- On tankless units, the serial is on a sticker on the right side of the cabinet (often beneath a QR code); older gas-tankless units used a silver plate on the lower-right front.
- On hybrid heat-pump units, the label is typically on the upper-left side.
- This decoder also works for Ruud and Richmond, and for older GE water heaters that Rheem built.
How to read a Rheem serial number
Rules last verified 2026-06-01On standard Rheem serials (no prefix, or a Rheem-family prefix like R, RH, RN, or RU), the first four digits are the build date: the first two are the month (01 through 12) and the next two are the two-digit year. Some Rheem lines instead use a week-and-year code marked by a single factory letter such as A, M, or Q — there the digits are a week, not a month. Rheem also prints no century, so treat the year as an estimate and confirm it with the “MFG. DATE” often printed on the rating plate.
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Look for the printed manufacture date first
Many Rheem, Ruud, and Richmond rating plates print a “MFG. DATE: MM/YYYY” next to the serial and model number. If it is there, that is your answer — no decoding needed.
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After any letters, read the first two digits for the month
On standard serials the prefix is empty or a Rheem-family code (R, RH, RN, RNG, RU). The first two digits after it are the month, 01 (January) through 12 (December). Heads up: a single factory letter such as A, M, or Q instead marks a week-and-year code — the decoder flags those so you don't read a week as a month.
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Read the next two digits for the year
The third and fourth digits are the two-digit year. For example, 1209 is December 2009 and 0806 is August 2006. Since there is no century digit, assume the most recent plausible year and confirm with the printed date.
Other Rheem serial styles (don't force the month-year read)
If the first two digits after the letters are larger than 12, or the serial uses dots, it is not the standard month-year code. Read the printed MFG date or use the official lookup instead.
| Serial example | What it is |
|---|---|
| RHUN M181401735 | Week-based style: after the letters, the first two digits ('18') are a week, not a month. Routed to verification. |
| A141511869 | Week-based style: '14' is a week, not a month. Read the printed date or verify. |
| 05.05-000021 | Tankless dotted style: references disagree whether it is month.year or year.month, so we don't guess it — read the printed date. |
| 09815101633 | Older all-numeric serial that doesn't follow the month-year code; date it from the printed plate, model era, or building age. |
Worked examples
1209D01234 12 is the month (December); 09 is the year 2009; D is the plant line. Built December 2009. (Rheem's own example.)
RH0806B17262 Skip the RH prefix. 08 is August; 06 is 2006. Built August 2006 — and this plate also printed “MFG. DATE: 08/2006”.
0801J03118 08 is August; 01 is 2001. Built August 2001 — an illustrative example of the bare month-year form with no letter prefix.
Rheem, Ruud, and Richmond — one date code
Ruud and Richmond are Rheem brands and use the very same serial date code, so this decoder works for all three; older GE water heaters that Rheem built decode the same way. You will also see the same scheme on Rheem-made retail lines such as Performance and Performance Platinum (The Home Depot), EcoSense, Professional, and Sure Comfort. Rheem's gas tankless units (also sold as Paloma) use a different, often dotted, date format — read the printed MFG date for those.
What your manufacture date tells you
Warranty
Rheem residential tanks come in warranty tiers, commonly 6, 9, 10, or 12 years, and the number in the model name usually signals the tier. Coverage generally starts on the documented installation date; when install proof is missing, Rheem's policy falls back to the manufacture date plus about 90 days — which is exactly why the serial's date matters. Enter your serial in Rheem's Warranty Verification tool for the exact coverage.
Check warranty by serial at Rheem ↗
How long they last and when to replace
Rheem says tank water heaters typically last 8 to 12 years, and that once a unit is 10 or more years old with recurring problems — or a repair would cost more than half of a new heater — replacement is usually the better investment.
Home inspectors generally treat 10 to 12 years as the typical service life for a tank water heater and often flag units past 12 years at sale. (Industry guidance.)
Rheem says tankless units can last 15 to 20+ years with proper care and descaling.
Watch for these replacement warning signs:
- Age past 10 to 12 years. At or beyond typical tank service life; budget for a replacement.
- Repair over half the replacement cost. Rheem's own 50% rule: replacing usually beats a major repair on an older unit.
- Rusty hot water. Discoloration from the hot tap can signal internal tank corrosion.
- Leaks at the base. Water around the base needs immediate attention and often means the tank is failing.
Why the age matters
Rheem recalls and your serial
Rheem's recalls are model-specific rather than one brand-wide action. The largest recent one: about 54,000 Rheem “Performance Platinum” electric water heaters (40, 50, and 80 gallon) sold only at The Home Depot were recalled in 2016 because the control panel can overheat.
- Affected models
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Performance Platinum electric, 40 / 50 / 80 gallonModels XE40M12EC55U0, XE50M12EC55U0, XE50T12EC55U0, XE80T12EC55U0 - Affected serials
- Affected serials use a factory letter + week + year: A0114–A5214, M0114–M5214, and Q0114–Q5214 (weeks of 2014), plus A0515 and A1015–A1615 (early 2015) — built January 2014 through April 13, 2015. CPSC recall 16-177, announced May 26, 2016.
- Hazard
- The control panel can overheat, posing a fire and burn hazard.
- Remedy
- Stop using the unit and contact Rheem for a free repair by a Rheem technician at (866) 369-4786, or see rheem.com Recall Information.
Other Rheem recalls exist: about 42,200 Power Vent 199,900 BTUH tankless units (Rheem RTG-74PVN/PVP, Ruud RUTG-74PVN/PVP, Richmond RMTG-74PVN/PVP, Rheem-Ruud GT-199PV, and Paloma models, sold 2004–2006) were recalled in 2007 over a carbon-monoxide risk (CPSC 07-108), and the 2005 Robertshaw R110 gas-valve recall covered Rheem-family units. Search the CPSC site by your model if it falls outside the range above.
Read the official CPSC recall notice ↗ Recall list last checked 2026-06-01
Can't read the serial number?
If the rating plate is corroded, painted over, or missing, try these in order.
- Read the “MFG. DATE” printed on the rating plate — Rheem often prints it outright, which avoids decoding entirely.
- If the plate is damaged, check a building permit, install sticker, or service tag for an installation date as a rough age.
- Enter the serial in Rheem's Warranty Verification tool to confirm the build date and coverage.
Model number vs serial number
Don't confuse the model number with the date. The number in a Rheem model name (such as a 6, 9, or 12) signals the warranty tier, not the build year. Likewise, an ANSI standard year printed on the plate is when the standard was published, not when your unit was made. Only the serial number's month-and-year digits — or a printed MFG date — give the actual age.
Frequently asked questions
How do I tell the age of my Rheem water heater?
Read the first four digits of the serial number after any letters: the first two are the month and the next two are the year (for example, 1209 = December 2009). Even easier, many Rheem plates print a “MFG. DATE” outright. Enter your serial in the decoder above for an instant estimate.
Is the Rheem serial month-then-year or year-then-month?
Month first, then year. Rheem's official format is MM (month) then YY (year): 0806 is August 2006, not June 2008. Reading it backwards is the most common mistake.
Rheem only gives a two-digit year — how do I know the century?
Rheem prints no century digit, so the two-digit year is an estimate. A unit still in service is almost always from the most recent plausible decade, but the surest check is the “MFG. DATE” printed on the rating plate or Rheem's warranty lookup.
Do Ruud and Richmond water heaters use the same code?
Yes. Ruud and Richmond are Rheem brands and use the identical month-and-year serial date code, and older GE water heaters that Rheem built decode the same way. This decoder works for all of them.
My Rheem serial doesn't start with a valid month — what now?
Some Rheem lines use a week-and-year code, often marked by a single factory letter such as A, M, or Q, and tankless units use a different, sometimes dotted, format. The decoder flags those — and any first two digits larger than 12 — instead of forcing a month-year read. For them, use the printed MFG date or Rheem's lookup.
How do I read a Rheem tankless serial number?
Rheem gas tankless units (also sold as Paloma) use a different date format from tank models, and references disagree on its order, so the safest answer is the “MFG. DATE” printed on the unit or Rheem's warranty verification tool.
Where is the serial number on a Rheem water heater?
On the rating plate. On tanks it is usually on the side, often lower down; on tankless units it is a sticker on the right side (often under a QR code); on hybrid heat-pump units it is on the upper-left side.
Does the model number tell me the age?
No. The number in a Rheem model name signals the warranty tier (for example 6, 9, or 12 years), not the build year. Only the serial's month-and-year digits — or a printed MFG date — give the age. An ANSI year on the plate is the standard's publication year, not your unit's age.
How does Rheem decide when my warranty started?
Coverage generally starts on the documented installation date; when install proof is missing, Rheem's policy falls back to the manufacture date plus about 90 days. That is why the serial's date matters. Use Rheem's Warranty Verification tool for the exact coverage.
How long do Rheem water heaters last?
Rheem says tanks typically last 8 to 12 years and tankless units 15 to 20+ years with care. Rheem also suggests replacing rather than repairing once a fix would cost more than half the price of a new unit.
Was my Rheem water heater recalled?
Rheem's recalls are model-specific. About 54,000 “Performance Platinum” electric units (40/50/80 gallon) sold at The Home Depot were recalled in 2016 for an overheating control panel, and some 2004–2006 Power Vent tankless units were recalled in 2007 over carbon monoxide. Check your model against the CPSC notices linked below.
Sources & verification
The serial and date-code rules and examples are sourced below — from manufacturer and inspector references — with recall data from the CPSC. Edge-case formats and broader context (lifespan, inspection, insurance, code) are separately sourced too. Confirm an individual unit with the official lookup.
Official: the rating-plate serial is 10 digits read as MM (month) + YY (year) + plant-line letter + 5-digit sequence. Example 1209D01234 = December 2009 (month 12, year 09, plant D).
Official Rheem guidance for determining equipment age from the serial number.
Official tool that returns warranty status and coverage from the serial number; routes to rheem.registermyunit.com.
Rheem: tank water heaters typically last 8–12 years; tankless can last 15–20+ years with care; if a repair exceeds 50% of replacement cost, replacement is usually the better investment.
Documents multiple Rheem serial styles: most are MMYY after a letter prefix (R, RH, RHLN, RHNG, RHUN, RU…); some are week-based (week in digits 1–2); a dotted tankless style appears. Lists Rheem family: Ruud, Richmond, Paloma, GE, Eclipse, Vanguard.
Corroborates MMYY across 1980s–present examples (R 0884B10488 = Aug 1988; RH 0806B17262 = Aug 2006 with a printed 'MFG. DATE: 08/2006'); documents the Rheem-built brand family (Ruud, Richmond, GE, Vanguard, Professional, etc.) and plate locations.
Recall 16-177 (May 26 2016): ~54,000 Rheem 'Performance Platinum' 40/50/80-gallon electric water heaters sold exclusively at The Home Depot (Jan 2014–Apr 2016); control panel can overheat (fire/burn). Models XE40M12EC55U0, XE50M12EC55U0, XE50T12EC55U0, XE80T12EC55U0. Free repair; Rheem 866-369-4786.
Recall 07-108 (Feb 21 2007): ~42,200 Power Vent 199,900 BTUH tankless units sold as Paloma, Rheem, Ruud, Rheem-Ruud, and Richmond (sold May 2004–Dec 2006); air-filter-door switch malfunction risks carbon monoxide. Free repair; Rheem 866-369-4786.