Water leaking from the bottom of the furnace or nearby pipework.

Safety: Turn off power if water is leaking onto electrical components. For gas appliances, avoid submerging any gas controls.

• Identify leak source: Dry the area and observe where water reappears: from a pipe joint, relief valve, condensate hose, or inside the casing.
• Check pressure relief valve: If water drips from the relief valve discharge pipe, system pressure may be too high or the valve may be faulty.
• Condensate leaks: Inspect the condensate trap and hoses for cracks or loose connections; reseat or replace as needed.
• Corrosion signs: Rust streaks on the heat exchanger or inside casing indicate internal leaks that require professional replacement.