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A-1 Mechanical Blog

Why Is My Furnace Flue Pipe Rusting?


When you look at your furnace, you’ll notice a large pipe sticking out of it that leads into a wall or ceiling. From the outside of your house, you may notice a pipe sticking out of your roof. Both of these pipes are your furnace flue pipes. They exhaust water vapor, carbon monoxide, and other gasses from your home. These pipes are essential for keeping the air flowing in your home and making sure toxic gases do not harm you or your family. If you notice that either one of your Furnace Flue Pipes Rusting, this could be a sign of worse problems to come.

A-1 Mechanical Heating & Cooling is your furnace and heating specialist. Repairing or replacing a furnace flue pipe could involve climbing on your roof or getting dirty. It’s best to trust the professionals to inspect your furnace as well when you notice any sort of rust in your HVAC system.

Why is My Furnace’s Flue Pipe Rusting?

There are a few reasons your furnace’s flue pipes are rusting. Ideally, combustion within a furnace would have two side effects: water vapor and carbon dioxide. However, no furnace is 100% efficient, and in every furnace some portion of the gas fails to combust entirely. This partial combustion results in the creation of byproducts like carbon monoxide and other toxic gasses. These gases are pushed through the furnace flue pipes and exhausted from the home.

When your furnace isn’t burning gas as efficiently as it could, there may be more byproducts being created in your furnace than you realize. These byproducts have chemical reactions with your exhaust pipes, causing them to rust.

Another reason why your furnace flue pipes are rusting is because there is an imbalance in the air to fuel mixture in your furnace. This could happen if you have a new furnace that is not compatible with your flue pipes, or there is insufficient pressure differential causing gases to have difficulty leaving your home. Rusty furnace flue pipes might just need to be replaced, or they could be a telling sign about the performance of your furnace.

I Have Rusty Furnace Flue Pipes

Furnace flue pipes aren’t always easy to see. If you’ve noticed strange odors in your house when your heat is on, or lack of airflow in your house, it’s best to inspect your furnace flue pipes. One should be attached from the furnace to the wall. Another might be on your roof. If you find rust on either, they could be a sign of issues that should be addressed immediately.

Rusted furnace flue pipes are more common in older homes and could be a sign of an aging HVAC system. If you had a new furnace installed recently, your pre-existing flue pipes might not be compatible with your new system. The best thing to do is to replace your pipes right away. Luckily, this is a relatively inexpensive fix, and it can prevent a dangerous situation in the future.

What If I Don’t Replace My Rusty Furnace Flue Pipes?

Think about rust on a car. You can slow down the growth of additional rust, but you can’t make the rust go away. It will get worse and corrode parts of your car. The same thing can happen with rusty pipes. Not only is rust unsightly, it can corrode and prevent toxic gases from leaving your house.

If toxic gases like carbon monoxide leak into your house, the results could be deadly. This is why you shouldn’t put off replacing rusty pipes. To prevent rusting in your HVAC system, it’s important to have it regularly cleaned and inspected to keep it running efficiently and safely.

Call A-1 Mechanical for Your Furnace and Heating Services

A-1 Mechanical is here for all your HVAC services. Whether it’s inspecting and replacing rusted furnace flue pipes, or replacing your furnace, trust the pros at A-1 Mechanical for all your heating and cooling needs.

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