Where to look: Rating label on the cabinet (side or bottom of the unit). Read it from the outside. If the label isn’t visible without removing a panel, don’t open the unit; use the installation paperwork or ask the installer.
Decode a Rinnai serial number
How to read a Rinnai serial number
Year letter + month letter (2009+), YY.MM (older) Since 2009: first letter = year (A = 2009 … H = 2016, J = 2017 … N = 2021, P = 2022 (O on one 2022 model), R = 2023, S = 2024, T = 2025, W = 2026), second letter = month (A–M, no I). Before 2009: YY.MM, e.g. 04.03-… = March 2004.
| Example serial | How it reads | Built |
|---|---|---|
BL.CA-051306 | B = 2010, L = November | November 2010 |
TB.AB-000001 | T = 2025, B = February | February 2025 |
04.03-123456 | 04 = 2004, 03 = March | March 2004 |
- Year letters start at A for 2009 and skip some letters: H is 2016, J 2017, N 2021, P 2022, R 2023, S 2024, T 2025 and W 2026. One 2022 model uses O instead of P. Month letters run A to M without I.
- The serial is usually on the rating label on the side or bottom of the cabinet, not on the remote controller. On some units the label sits behind a front access panel; don’t open the unit to read it. Use the installation paperwork or registration record, or ask the installer.
- Rinnai does not publish this format itself. It comes from two independent references (Building Intelligence Center (opens in a new tab) and Parts Town (opens in a new tab)) that agree on the letter sequence, so confirm a borderline result with Rinnai before relying on it for warranty.
Format source: Building Intelligence Center: Rinnai water heater age (opens in a new tab); also Parts Town: Rinnai serial number lookup (opens in a new tab).
What to do with the date
- Check the warranty. Check the terms for your model on Rinnai’s warranty page (opens in a new tab), and register the unit (opens in a new tab) if it isn’t already. Rinnai’s page has no serial-number lookup, so ask Rinnai or the installer to confirm coverage. Coverage depends on the model and the build or installation date.
- Weigh repair against replacement. Age is one factor; leaks from the tank, rusty hot water and repeated failures matter more. See how long water heaters last and the repair-or-replace notes on the main decoder page.
- Troubleshoot by brand. Our Rinnai guides cover codes, lights, leaks and no-hot-water problems.
Common questions
Does the age matter on a tankless heater?
Less than on a tank, because most tankless parts can be replaced. The heat exchanger warranty and the cost of a heat exchanger repair are usually what decide repair or replace on an older unit.
My Rinnai serial has no dots or dashes. Does that matter?
No. The decoder ignores spaces, dots and dashes; type the characters in order.
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