Defro Condensate Management / Flue Condensation Issue

Boiler flue terminal drips water or white staining appears on the wall below the terminal.

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Safety Warning

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

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Possible Causes

Incorrectly sloped Defro flue causing condensate to run to terminal, Blocked condensate trap or drain on Defro boiler, Damaged flue seals allowing condensate leakage, Excessive flue length without proper support

How to Fix / Troubleshooting

Safety: Flue work must comply with regulations; major changes should be done by a qualified installer.

  • Check condensate drain: Ensure the condensate pipe from the Defro boiler to the drain is not blocked or frozen. Clear any obstruction and lag external sections in cold climates.
  • Inspect trap: Clean the condensate trap under the boiler, removing sludge and refilling with clean water.
  • Flue slope: Visually check that the horizontal flue section slopes slightly back towards the boiler, not towards the terminal.
  • Seal inspection: If water appears at flue joints, a technician should disassemble and reseal the flue with new Defro-approved seals.
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Repair Difficulty

Medium 3/5

Required Part

Defro condensate trap
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