Unit shuts down and displays Code 25; may be accompanied by a fuel smell or abnormal combustion noise

Safety first: Turn OFF power and gas. Condensate may be acidic; wear gloves and eye protection when handling drain components.

Steps to check:

• Inspect condensate drain: Locate the condensate drain line at the bottom of the unit. Ensure the line is not kinked, blocked, or frozen. Clear any visible obstructions.
• Check trap: Verify the condensate trap is properly filled with water and not cracked or leaking.
• Verify vent slope: Ensure horizontal vent sections slope back toward the heater or per Rinnai instructions so condensate can drain.
• Reset and test: After clearing the drain, restore power and gas, reset the unit, and observe operation.

When to call a professional: If Code 25 persists, a technician should inspect the condensate system, venting, and combustion settings.