Water heaters / Rinnai

How old is my Rinnai water heater?

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Where to find the serial number

Rating label on the side of a tank water heater
Close-up of a rating label showing the serial numberOn tankless models, check the side or lower edge of the cabinet

Rinnai serial formats we can read

Dark = year, orange = month or week.

Year and month letters

BL.CA-051306

November 2010.

Legacy year.month

04.03-102521

March 2004.

Legacy numeric year/month

05083453

August 2005.

Coverage and sources

Supports the CA letter layout and the two displayed legacy numeric layouts; other modern factory suffixes are not yet covered.

References checked 2026-10-26.

Independent reference tool, unaffiliated with Rinnai. Sources & method