Flue Testing Procedure

Outline

Before a solid fuel appliance can be installed into a pre-existing masonry chimney the flue must be tested to determine its condition. A pre-existing masonry flue can be used with a solid fuel appliance if none of the following defects are found during testing:

• Smoke leakage into habitable space/adjoining flues (greater than 2 litre/s/m²)
• Narrowing of the flue from original diameter
• Complete blockage of the flue
• Alterations to the chimney that compromise its masonry
  
  All of these outcomes are tested for in the following tests according to ADJ. As a general rule, if a property has had a loft conversion, a flue liner is recommended as the building work often compromises the chimney masonry.

Testing

Coring ball test

This test determines whether the flue has a constant diameter throughout its full length and indicates any blockages and their location. A heavy coring ball with a diameter of no less than 25mm of the **required flue diameter** is lowered on a rope from the flue outlet (highest point) to the bottom of the flue.

Smoke Test I

The purpose of carrying out Smoke Test I (Pressure Integrity Test) us to check that flue gases will rise freely through the flue and to identify whether there are any faults, such as incorrectly sealed joints or damage that would cause the flue gases to escape into habitable space / adjoining flues.

• All windows and doors in the room served by the flue are closed.
• The flue is heated for up to 10 minutes to ensure an adequate draw.
• Smoke pellet(s) are lit and placed at the opening of the flue.
• Once smoke is seen issuing freely from the outlet (highest point) of the flue it is sealed.
• The full flue length is then checked for any significant leakage (greater than 2 litre/s/m²).
• The test should be allowed to continue for 5 minutes.
• The closures at the top and the bottom of the flue should then be removed.
  
  If smoke is seen to leak between flues at chimney stack height this may be remedied by repairing any cracks/holes in the feathering between adjoining flues. In these cases, a liner is not necessarily needed and a quote will be given for repair of the chimney stack.
  
  These tests will determine the current state of the flue but offer no guarantee to how long the flue will remain in that state. The majority of flues in house built since the 30s will be of sound condition especially if they have been fit with gas appliances and subsequently gas liners but these tests can only assess the flue in its current state. However, with a liner installed it can be assumed that the condition of the flue will remain intact for the manufacturers guaranteed life of the liner although this relies on good practice with solid fuel and annual sweeping.