What does error code 79 mean on a Rinnai tankless water heater?

Water leakage detected. The leak detector found water inside the heater's cabinet.

Can I fix Rinnai code 79 myself?

Start with these safe checks: Turn off the heater and look under it and around the pipes for water. Rinnai's checks inside the cabinet are for professionals. If water is leaking, shut off the water supply to the heater and call a plumber.

When should I call a technician for code 79?

Rinnai's checks inside the cabinet are for professionals. If water is leaking, shut off the water supply to the heater and call a plumber. Smell gas? Leave right away, don't touch light switches or phones inside, and call your gas utility or 911 from outside. Never open a gas valve, burner, gas line, vent or flue connection, or bypass a safety switch. Repeated lockouts, scorching, soot, or a CO alarm mean shut it off and call a licensed gas technician.

Rinnai Tankless Water Heater Error Code 79: Water leakage detected

What 79 means

The leak detector found water inside the heater's cabinet.

Likely causes

Leaking heat exchanger or internal piping
Condensation in the cabinet

Safe first checks

Turn off the heater and look under it and around the pipes for water.

When to stop

Rinnai's checks inside the cabinet are for professionals. If water is leaking, shut off the water supply to the heater and call a plumber.

Checked against: Rinnai: Troubleshooting Tankless Water Heater Diagnostic Codes (100000652). Codes can differ by model and year, so confirm with your owner's manual.