Water heater runs but produces excessive white steam or vapor from the flue terminal.

Safety: Observe from a safe distance. Do not touch hot flue components.

• Assess conditions: In cold weather, a visible white plume can be normal condensate vapor. Compare with manufacturer expectations.
• Check condensate drain: Ensure the condensate trap and drain line are clear and draining properly.
• Inspect combustion: Have a technician perform a combustion analysis to verify correct CO2/O2 levels and adjust gas valve if necessary.
• Check for water in flue: If condensate backs up, it can partially flood the heat exchanger. Correct drain issues and inspect for damage.