Boiler Flue Problem or Blockage
Staining around the flue terminal, condensation streaks on the wall, or a boiler locking out on a flue-related code..
Staining around the flue terminal, condensation streaks on the wall, or a boiler locking out on a flue-related code.
What is actually going on
Staining around the flue terminal, condensation streaks on the wall, or a boiler locking out on a flue-related code.
The realistic causes, in order
A blocked or partially obstructed flue terminal, including nests and debris Failed flue seals or a joint that has pulled apart inside a void An air pressure switch or differential sensor detecting incorrect flue conditions
What we test on site
Flue integrity along its full length, including inspection hatches where the flue runs in a void Combustion analysis at the appliance Terminal position against the manufacturer's and Gas Safe clearance requirements
Get a flue problem diagnosed properly
Flue repairs must restore the manufacturer's specified arrangement exactly; nothing about a flue is improvised.
Questions we get asked
What causes a flue problem on a gas boiler?
A blocked or partially obstructed flue terminal, including nests and debris
What normally puts a flue problem right?
Flue repairs must restore the manufacturer's specified arrangement exactly; nothing about a flue is improvised.
Is it safe to keep using the system with a flue problem?
Flue faults can allow combustion products into the property. This is the one category on this site we treat as an immediate safety matter — turn the boiler off and get a Gas Safe engineer out. If anyone feels unwell, ventilate, leave and seek medical advice.