Rinnai Water Heater Age: Serial Number Decoder
Rinnai mainly makes tankless water heaters, and on units built since 2009 the first two letters of the serial number are the build date: the first letter is the year and the second is the month. Older units (1999–2008) use four digits in year-then-month order. One honest caveat up front: the letter table is an inspector convention rather than a current official Rinnai lookup, so treat the result as an estimate and confirm with the manufacture date printed on the unit.
How old is my Rinnai water heater?
On units made since 2009 the first two letters are the build date: the first letter is the year and the second is the month. Type your serial for an instant estimate, or read the printed manufacture date on the plate.
e.g. Where's my serial number?
Standard Rinnai tankless models use this code. Some specialty or non-standard units may use a different serial format.
Where to find your serial number
- Look on the rating/specification plate, typically on the side panel of the tankless cabinet or near the lower front access area; the exact spot varies by model.
- Many Rinnai plates print the manufacture date directly — read that first, since the letter code is only an estimate.
- This decoder is for Rinnai tankless units; a tankless badged Bradford White (EverHot), GE, or Giant may be Rinnai-built and can carry the same letter code.
How to read a Rinnai serial number
Rules last verified 2026-06-01On Rinnai units made since 2009, read the first two letters of the serial: the first is the year (A=2009, B=2010, … through the table below) and the second is the month (A=January through M=December, skipping I). Units from 1999–2008 instead use four digits in year-then-month order. The letter table is inspector-derived and the post-2020 codes are disputed, so confirm the year against the printed manufacture date.
-
Find the rating plate (and the printed manufacture date)
The serial is on the rating data plate, usually on the side panel or near the lower front of the tankless cabinet. Many plates also print the manufacture date outright, which is the surest answer.
-
Read the first letter for the year
On units made since 2009 the first letter is the year: A=2009, B=2010, C=2011, on up. The code skips the letters I, Q, U, and V. Use the year-code table below to look yours up.
-
Read the second letter for the month
The second letter is the month: A=January, B=February, on through M=December, skipping the letter I. So a serial beginning “CD” is C (2011) and D (April) — April 2011.
-
Older unit? Read the four digits instead
A serial that starts with digits is a pre-2009 unit: the first two digits are the year (for example 05 = 2005) and the next two are the month, sometimes separated by a dot, as in 05.04 = April 2005.
Rinnai year-letter codes (first letter, 2009 onward)
The first letter of a post-2009 serial. The code skips I, Q, U, and V. These codes are inspector-derived, and 2021-and-later (N onward) are disputed between references — confirm against the printed manufacture date.
| Letter | Year |
|---|---|
| A | 2009 |
| B | 2010 |
| C | 2011 |
| D | 2012 |
| E | 2013 |
| F | 2014 |
| G | 2015 |
| H | 2016 |
| J | 2017 |
| K | 2018 |
| L | 2019 |
| M | 2020 |
| N | 2021 (disputed) |
| O / P | 2022 (disputed) |
| R | 2023 (disputed) |
| S | 2024 (disputed) |
| T | 2025 (disputed) |
| W | 2026 (disputed) |
| X | 2027 (disputed) |
| Y | 2028 (disputed) |
| Z | 2029 (disputed) |
Rinnai month-letter codes (second letter)
The second letter of a post-2009 serial. A=January through M=December, skipping the letter I.
| Letter | Month |
|---|---|
| A | January |
| B | February |
| C | March |
| D | April |
| E | May |
| F | June |
| G | July |
| H | August |
| J | September |
| K | October |
| L | November |
| M | December |
Worked examples
CD.CA-061205 C is the year 2011; D is the month April. Built around April 2011. (The “CA” and digits that follow are not part of the date.)
BL.CA-051306 B is the year 2010; L is the month November. Built around November 2010.
05.04-103630 An older pre-2009 unit: 05 is the year 2005 and 04 is the month April. Built around April 2005.
Rinnai is mostly tankless — and builds some other brands' tankless units
Rinnai is best known for tankless (and condensing) water heaters, though it now also offers REHP-series electric heat-pump tank water heaters and the Demand Duo hybrid, which pairs a tankless engine with a storage tank. Those tank-type and hybrid units may use a different serial scheme, so confirm them against the printed plate. Rinnai has also built OEM tankless units for other brands — Bradford White (the EverHot line) and GE since 2006, and Giant since 2012 — so a tankless unit wearing another badge may actually be a Rinnai with this same letter date code. Because Rinnai does not provide a current public date-code lookup for this serial style, always confirm an important date against the printed manufacture date or Rinnai support.
What your manufacture date tells you
Warranty
Rinnai residential tankless warranties commonly run 12 to 15 years on the heat exchanger and 5 years on parts depending on the model series (current SENSEI units list a 15-year heat exchanger). Labor is 1 year, extending to 5 years if you register within 90 days of purchase — though California and Quebec do not require registration to get the longer terms. Coverage runs from installation, so registering also records that date. Check or register coverage through Rinnai's registration page with your serial number.
Check warranty by serial at Rinnai ↗
How long they last and when to replace
Rinnai says a tankless water heater's life expectancy is up to 20 years — roughly twice a tank heater — depending on water quality, usage, and maintenance.
In practice, 15 to 20 years is the common range with regular maintenance; hard water and skipped descaling shorten it. (Industry guidance.)
Rinnai recommends flushing the unit to remove mineral scale at least once a year (more often in hard water). Skipping it is a leading cause of early tankless failure.
Watch for these replacement warning signs:
- Age past 15 to 20 years. At or beyond typical tankless service life; start planning a replacement.
- Recurring error codes. Repeated fault codes or lockouts on an older unit can signal a failing heat exchanger or controls.
- Declining hot water or scale. Falling output or scale at the fixtures often means the heat exchanger needs descaling — or is near end of life.
- Leaks from the unit. Water from the cabinet needs immediate attention and can indicate a cracked heat exchanger.
Why the age matters
Can't read the serial number?
If the rating plate is corroded, painted over, or missing, try these in order.
- Read the manufacture date printed on the rating plate — it is more reliable than the letter code, which is only an estimate.
- If the plate is damaged, check a building permit, install sticker, or your registration record for an installation date.
- Contact Rinnai support with the model and serial number to confirm the build date, especially for 2021-or-later units.
Model number vs serial number
Don't confuse the model number with the date. A Rinnai model name (such as RL75, RU199, RUR199, or a SENSEI number) identifies the series and flow rate, not the build year. Only the serial's first two letters — or the printed manufacture date — give the age.
Frequently asked questions
How do I tell the age of my Rinnai water heater?
On units made since 2009, read the first two letters of the serial number: the first is the year and the second is the month. Enter the serial in the decoder above, or read the manufacture date printed on the rating plate, which is the surest check.
Which letter is the year and which is the month?
The first letter is the year (A=2009, B=2010, and so on) and the second letter is the month (A=January through M=December, skipping I). So a serial starting “CD” is 2011 (C), April (D).
My Rinnai serial is all numbers — how old is it?
That is the pre-2009 format. The first two digits are the year (for example 05 = 2005) and the next two are the month, sometimes with a dot, as in 05.04 = April 2005. The decoder handles this automatically.
How reliable is the Rinnai letter date code?
Treat it as an estimate. Rinnai does not publish the letter table — it comes from home-inspector references — and the codes for 2021 and later are disputed between sources. For an important date, confirm against the printed manufacture date or Rinnai support.
Is my Bradford White, GE, or Giant tankless actually a Rinnai?
It might be. Rinnai has built OEM tankless units for Bradford White (the EverHot line) and GE since 2006, and Giant since 2012. If a tankless unit under one of those brands has a serial that starts with two letters, this Rinnai decoder may apply — but confirm with the printed date or the badged brand.
Where is the serial number on a Rinnai tankless unit?
On the rating plate, usually on the side panel of the cabinet or near the lower front access area. The exact spot varies by model; many plates also print the manufacture date.
How long do Rinnai tankless water heaters last?
Rinnai says up to 20 years — about twice a tank heater — with 15 to 20 years common in practice. Lifespan depends heavily on water quality and on flushing the unit at least once a year.
Do I really need to descale or flush my Rinnai every year?
Yes. Rinnai recommends flushing mineral scale at least once a year, and more often in hard water. Skipping it is a leading cause of early tankless failure, so the age of a unit matters less if it has been flushed regularly.
What is the Rinnai warranty, and do I have to register it?
Residential tankless coverage commonly runs 12 to 15 years on the heat exchanger and 5 on parts depending on the model (SENSEI units list 15 years), with 1 year of labor that extends to 5 if you register within 90 days. California and Quebec don't require registration for the longer terms. Registration also records your installation date.
Was my Rinnai water heater recalled?
No CPSC recall covers any Rinnai water heater. Rinnai recalls on record are for other products — i-Series Plus gas boilers (2025) and EnergySaver wall furnaces (2008) — and the 2015 tankless recall was a different brand (Coaire/Quietside), not Rinnai. Check Rinnai's recalls hub if unsure.
Does Rinnai make tank-type water heaters?
Mostly Rinnai makes tankless units, but it now also offers REHP-series electric heat-pump tank water heaters and the Demand Duo hybrid (a tankless engine with a storage tank). Those tank-type units may use a different serial scheme, so confirm them against the printed manufacture date rather than the letter code.
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.
Documents Rinnai's serial styles: since 2009 the first letter = year and second letter = month (A=2009…M=2020, N=2021, O&P=2022, R=2023…, skipping I/Q/U/V; months A=Jan…M=Dec skipping I); pre-2009 units use YYMM digits (with or without a dot). Also: Rinnai began building OEM tankless for Bradford White and GE (2006) and Giant (2012).
Inspector reference; documents the pre-2009 numeric YYMM date scheme and Rinnai support/contacts. Notably does NOT publish the Style-1 letter table, underscoring that the letter codes are unofficial.
Official: Rinnai residential tankless units carry 1-year labor coverage, extendable to 5 years if the product is registered within 90 days of purchase (heat-exchanger and parts coverage run longer, commonly 12 and 5 years, varying by model).
Official product-registration page; registration within 90 days extends labor coverage and records the install date.
Official: a Rinnai tankless water heater's life expectancy is up to 20 years, and Rinnai recommends flushing mineral deposits at least once a year (more often in hard water).
No CPSC recall covers any Rinnai water heater. Rinnai recalls on record cover other products: i-Series Plus gas BOILERS (CPSC 25-313, 2025, CO hazard) and EnergySaver direct-vent WALL FURNACES (2008, CO hazard). The 2015 'tankless water heaters' recall was Coaire/Quietside, not Rinnai.