Condensate drain gurgles loudly and occasionally backs up

Safety: Condensate is mildly acidic; wear gloves.

• Clean trap: Remove and flush the condensate trap to clear sludge.
• Check slope: Ensure the condensate pipe runs downhill continuously with no upward loops.
• Vent line: If allowed by local codes, provide an air break or vent to prevent siphoning.
• Monitor: After cleaning, run the furnace and confirm steady condensate flow without backing up.