Boiler leaking water from bottom of cabinet

Safety: Turn off power and close the boiler isolation valves if present. Hot water can cause burns; allow the unit to cool before inspection.

• Identify leak source: Remove the front panel and use a flashlight to trace water back to its origin. Check around the heat exchanger, pump flanges, relief valve, and condensate components.
• Relief valve check: If water is dripping from the relief valve discharge pipe, system pressure may be too high or the valve may be failing. Do not cap this pipe. A technician should test system expansion tank and replace the valve if needed.
• Tighten fittings: For minor seepage at unions or threaded connections, gently tighten with appropriate tools. Do not overtighten aluminum or brass fittings.
• Heat exchanger or major leak: If the Dettson heat exchanger or internal manifold is leaking, shut down the boiler and contact a professional. These components typically require specialized replacement.