Problems That Could Develop With Your Furnace Flue And The Repairs That Might Be Necessary

30 December 2020
 Categories: , Blog


If you have a gas furnace, the combustion gases have to be vented to the outside. This happens through the flue, which is also called the exhaust stack. The flue plays an important part in protecting you from hazardous gases, such as carbon monoxide. It might be difficult to tell when something is wrong with the flue, but you might have some clues. Here are signs the flue is malfunctioning and the furnace repairs that could fix the problem.

Signs Of Problems With The Exhaust Stack

If airflow is restricted through the stack, this can have an effect on the way the combustion area in your furnace works. In a typical gas furnace, combustion gases are drawn up through the flue passively. If you have a high-efficiency furnace, the gases are blown out with a fan.

When there are problems with air movement through the flue, the furnace might start to short cycle. You might also notice a buildup of soot in the combustion area or even around your furnace. A blocked flue can even cause backdrafting, and a backdraft could cause condensation in the furnace that leads to rust.

Even if your furnace is serviced every year, it's a good idea to check it monthly when you change the filter to look for rust on the flue pipe, as that could be a sign of flue problems. Another sign of a bad flue is when your carbon monoxide alarm goes off. This indicates combustion gases are leaking into your house rather than flowing out the exhaust stack.

Reasons A Flue Gets Clogged Or Leaky

The main cause of a leaky flue pipe is rust. Rust can develop with age or when the pipe is exposed to water or condensation. A flue might also leak or get clogged if there is a problem with an elbow or other joint in the pipe.

The main cause of a clogged flue pipe is debris from animals. The pipe blows out warm air, so animals like to snuggle close to the pipe or even build nests in it. A bird's nest can cause a clog that leads to backdrafting and the inability of the flue to eliminate toxic gases.

Repairs That Could Be Needed

Furnace repairs shouldn't be put off when something is wrong with the flue due to the hazardous nature of carbon monoxide. Call a furnace repair company as soon as you suspect problems. The repairs might be as simple as cleaning out the flue to get rid of leaves or a nest. However, if the flue is bad, it should be replaced.

The flue might also need to be replaced if it turns out it's the wrong size, and the size mismatch is the source of your problems. This might happen the first winter after you have a new furnace installed.

The furnace repair technician will examine the flue and combustion area of your furnace to see what parts need to be replaced or repaired. When gases can't vent properly, other parts of the furnace can be affected. The repair technician might need to clean soot off the burners and off of the ignition area.

The technician will probably check the heat exchanger, too, since problems in the combustion area can have an effect on the cheat exchanger. Carbon monoxide flows through the heat exchanger too, so it's not safe to run your furnace if the exchanger is cracked or rusty.


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