Balanced And Conventional Flues

A flue is basically a tube which takes smoke and gas away from a fire, often through a chimney stack. Flues may be made from many materials including steel, stainless steel, cast iron, clay and concrete. Usually flues for oil-fired boilers are made from steel. They are available in a variety of diameters and lengths, 80mm, 100mm, 125mm and 150mm diameters, and lengths which range from 250mm to 1250mm.

Conventional flues rely on the natural circulation of heated air to take smoke and combustion gases away from the source of combustion, e.g. a fireplace, stove or gas or oil-fired boiler. The air required for combustion is drawn from the air surrounding the stove or boiler, it is not supplied by the flue. This is where balanced flues differ.


A balanced flue supplies air to the combustion source stove or boiler by means of a double skinned construction (think of a tube inside a tube). Combustion gases are drawn away from the boiler or stove through the flue, but the flue also allows air to be drawn into the boiler or stove from the outside. The boiler or stove does not require air from the room or area where it is situated.

A balanced flue may exit a building either vertically or horizontally. Usually a basic flue kit is added to with additional parts (e.g. bends) in order to achieve an exit which meets with statutory building regulations.

A competent plumbing or heating contractor will be able to advise you on the best flue for your heating system. In many cases it is possible to retain the aesthetics of a traditional chimney and get the safety and efficiency advantages of a balanced flue through installing a special flue liner in your existing chimney.

The experts at PD Plumbing Supplies will be able to explain to you which oil-fired boiler or stove would be the best option for your heating requirements and they will also advise on the correct flue to use.

Phone 028 711 400 24 from the UK or 074 93 61668 from Ireland. Email pdplumbingsupplies@gmail.com. You can also use the 'Chat' function on our web site: pdplumbingsupplies.com