Furnace Flue Pipes: Installation, Inspection, and Care

Furnace Flue Pipes: Installation, Inspection, and Care
Furnace flue pipes are crucial parts of furnaces. These important furnace components transfer dangerous fumes from a furnace to the outdoors so families breathe in safe air free of fumes. Fume inhalation can cause serious health complications and sometimes death, so keeping these dangerous gases outside is essential. Your furnace flue pipes will operate most efficiently when you properly maintain, regularly inspect and replace them when necessary. Continue reading to learn more about furnace flue pipes and how you can ensure your home is safe.

What Does a Furnace Flue Pipe Do?

The flue pipe's job is to transfer hazardous fumes from a furnace to outside the house. Furnace flue pipes are also known as furnace exhaust stacks or vents, and they are incredibly important for homes. Furnaces are combustion heating systems that use oxygen, heat and fuel to generate and release heat. As a furnace generates heat, it also releases noxious combustion gases such as carbon monoxide, nitrogen dioxide and sulfur dioxide. These gases can harm human health, making it incredibly crucial to direct these fumes outside of the home.

Why Are Furnace Flue Pipes Important?

Furnace flue pipes are important because they keep people safe from harmful gases. Carbon monoxide is a colorless, odorless gas that can poison people if it builds up inside a home or building. Breathing in carbon monoxide can cause flu-like symptoms such as the following:
  • Dizziness
  • Weakness
  • Chest pain
  • Headache
  • Upset stomach
  • Vomiting
  • Confusion
Carbon monoxide poisoning can also cause death if someone inhales enough of it. In some cases, people pass away from carbon monoxide poisoning without experiencing any symptoms. A furnace flue pipe is crucial for households with furnaces because it protects families from carbon monoxide exposure and prevents serious illness and death.

How Do Furnace Flue Pipes Work?

A furnace flue pipe safely transfers fumes outside the home so homeowners and their families do not breathe them in. It operates similarly to a fireplace chimney, which directs wood smoke up and outside the home before it can fill a room. A furnace flue pipe is a metal tube containing a damper that regulates the air pressure between the outside air and the air coming from the furnace. A flue pipe can be routed into a home's chimney or connected to an outlet point. The flue pipe's damper creates a draft that pulls gases from the furnace and up the stack where it vents to the outside. It also stops exhaust fumes from re-entering the furnace and dispersing throughout the home.

What Would Happen if a Furnace Flue Pipe Was Missing?

If a furnace flue pipe malfunctions or is missing from a furnace, fumes and carbon monoxide can circulate throughout the home. When exhaust gases enter a home, families will breathe them in and can potentially experience health complications or death as a result. Since carbon monoxide is odorless and colorless, families need to have furnace flue pipes and install carbon monoxide detectors to warn them if carbon monoxide enters the home.

Does My Furnace Flue Pipe Need to Be Replaced?

Corrosion, normal wear, weather, debris and bird's nests can damage furnace flue pipes. Temperature changes can cause pipes to expand and contract, leading to leaks. Additionally, insufficient airflow can prevent a flue pipe from accessing enough air, which forces it to draw combustion gases into the house. A worn or damaged flue pipe presents potential hazards because it can allow dangerous fumes into your home. Your furnace flue pipe may need to be replaced if you notice any of the following signs:
  • Rust
  • Cracking
  • Damage
  • Debris
  • Leaking
  • Insufficient heating
If your furnace is not heating your home properly or you notice a leak, your furnace flue pipe most likely needs to be replaced. However, signs that your flue pipe needs a replacement may sometimes be less obvious. When you check your flue vent for damage and rust, it's important to look at the entire length of the pipe. Examine the rain cap seals and the storm collar closely. The rain cap is the rounded piece that sits on top of the vent, and the storm collar is the rounded, bulging piece that sits above your home's roof. You can perform a visual inspection of your flue pipe using a ladder. Examining your flue pipe from the top allows you to see more of the pipe and check for potential debris, but you should make sure you practice safety while inspecting from the roof. Scheduling annual inspections and cleanings can keep your flue pipe in good shape and help you identify when you need a replacement.

How Much Does It Cost to Replace a Flue Exhaust?

The cost of exhaust pipe replacement partially depends on the type of furnace flue pipe your furnace needs. Flue pipe replacements cost more for older units than modern units. Newer units are typically more efficient than older ones and are less likely to need repairs or replacements. Speak with a professional to know your options if you need a replacement flue exhaust pipe.

Types of Furnace Vents

Natural, concentric and sidewall furnace vents have different designs and operate in different ways.

Direct vs. Non-Direct Vent Installations

Direct and non-direct vent installations operate differently in how they take air in and expel it outside. Direct vent installations are two-pipe systems, and they take combustion air from outside to discharge flue gases outside. Non-direct vent installations are single-pipe systems, and they take combustion air from inside a home, a ventilated crawlspace or an attic to discharge flue gases outside.

Natural Furnace Vents

Natural furnace vents are also known as type B vents, and they run vertically from a furnace and through a home's roof. In a natural furnace vent, exhaust fumes naturally rise and exit the pipe on their own. A natural furnace vent is cheaper than other options, but it is more likely to backdraft fumes in certain situations. Natural furnace vents work best for low-efficiency furnaces.

Concentric Furnace Vents

A concentric vent consists of two vent pipes of the same size fitted together. These pipes connect to a smaller inner pipe that moves fumes outdoors and a larger outer pipe that pulls fresh combustion air into the furnace. Concentric vents can be installed vertically and vent through a home's roof or horizontally and vented through a home's exterior wall. They are for high-efficiency furnaces.

Sidewall Furnace Vents

Sidewall furnace vents are also for high-efficiency furnaces, and a sidewall furnace vent uses a one or two-pipe system. In the sidewall furnace vent system, the intake and exhaust pipes run separately from each other. This system offers the most placement flexibility because the exhaust pipe can vent through almost any exterior wall or through the roof.

How to Install a New Furnace Exhaust Pipe

Furnace flue pipe installation requires precision to ensure proper ventilation, so it's important to hire an HVAC professional when your pipe needs to be replaced. A professional knows how to properly inspect furnaces, install furnace flue pipes and make sure they meet safety considerations and specific building codes. Trying to install a furnace exhaust pipe without a professional could result in improper installation and gas leaks in your home, so it's better to be safe and trust a professional with this process. HVAC professionals effectively install furnace flue pipes with the following steps:

1. Remove the Old Pipe

Before installing a new furnace exhaust pipe, an HVAC professional removes the old pipe. After removing the old flue pipe, they clean the flue and inspect furnace components such as the damper. They also inspect the chimney if the flue pipe connects to an existing chimney.

2. Determine the Correct Distance and Angles

Precise fitting is crucial to furnace exhaust pipe installation because it ensures a correct pressure differential. When the pressure differential is correct, it creates an effective natural draft, which lifts gases out of the furnace and sends them outside safely. HVAC professionals measure the distance from your furnace to the chimney or outlet point. They then use this distance measurement to determine which pipe angles will provide the most efficient and direct natural draft exhaust. A professional also understands the importance of a furnace and vent pipe's location. A proper vent installation depends on where a furnace is located within a home, as air may not vent properly if it has to travel a long distance. Additionally, it's crucial to install exhaust pipes away from chemicals because airborne chemicals can corrode the pipes.

3. Fit the Pipe to the Furnace and the Home's Chimney or Outlet Point

After determining the correct pipe angles, the HVAC professional cuts galvanized metal ductwork with the correct length and diameter to fit the furnace. They then begin installing the ductwork and pipe pieces by fitting each piece's crimped end to a non-crimped end, starting at the furnace. Four sheet metal screws secure each piece of piping, and high-temperature caulking seals the piping. To complete the installation, the HVAC professional uses galvanized steel straps to secure the flue pipe to the house framing. The galvanized steel straps reduce pressure on the pipe's joints to help them remain intact.

How to Clean and Maintain a Furnace Vent Pipe

To maintain your furnace and extend your flue pipe's life span, you should clean it every few months. Since different furnace models have different cleaning specifications, you should check your system's owner's manual to see if it has any restrictions, precautions or actions that will void its warranty. After checking for specific cleaning instructions and guidelines, you can clean your furnace vent pipe with the following steps:

1. Turn Your Furnace Off and Locate the Vent Pipe

Make sure your furnace is turned off before you begin to clean it. Next, you can locate the furnace flue pipe. Carefully use a ladder to access your roof or the exterior wall where the vent is located and look for a long tube of piping. The piping may be gray or white, and it should be topped with a circular cap. After locating the vent pipe, ensure you have all the necessary tools and safety gear. Eyewear and gloves will protect you from dust particles and any other debris you may encounter.

2. Remove the Vent Cap

Remove the vent cap using a screwdriver, so you can see inside. The following debris can become stuck in furnace flue pipes over time:
  • Ice
  • Dust
  • Bird nests
  • Natural debris

3. Remove Debris From the Vent Pipe

You can use your hand to remove as much debris as possible, but you can use a plastic hook or metal wire to clear any debris that is stuck or farther down the pipe. Next, you should scrub the inside of the pipe to remove any additional debris and dust. You can also use a handheld vacuum to remove as much debris as possible. Next, wipe the pipe clean with a soft cloth or rag before replacing the cap.

Troubleshooting — My Furnace Flue Pipe Is Clogged

A clogged furnace flue pipe can release harmful gases into your home, potentially causing health conditions such as carbon monoxide poisoning. If you notice your furnace running improperly or failing to operate, your furnace pipe may be clogged. If you cannot reach debris lodged in your flue pipe or remove debris from the pipe and still notice your furnace malfunctioning, you should contact a professional to inspect your system.

Troubleshooting — My Furnace Flue Pipe Is Leaking Water

If your furnace flue pipe leaks water or condensation, your flue pipe may need attention. Leaks can occur when a pipe is clogged, cracked or the incorrect size. Leaking can also occur when a pipe's joints are vulnerable. A condensation leak most likely means that gases are also leaking into your home, so it's important to address this situation as soon as possible. Fixing leaks is important because condensation buildup can cause corrosion over time, rusting and damaging your flue pipe. If you notice any leaks, you should call a professional to patch any holes as soon as possible.

Need a New Furnace? Contact Ingram’s Water & Air

Properly maintaining your furnace will extend its life span and keep your home warm and cozy longer. The flue pipe is an important part of a furnace because it keeps harmful gases out of your home so you breathe in only safe air free of fumes. Since fume inhalation presents serious health hazards and can lead to death, it's crucial to maintain your flue pipe and ensure it's working at all times. In some cases, you may need to replace your flue pipe or purchase a new furnace. Reliable home furnace systems will keep your home warm and your family safe. With an efficient home system, you can trust that your furnace is working properly and your flue pipe is effectively moving harmful gases outside your home. A furnace is an important investment, so choosing the right one for your home is essential. If you are a homeowner looking to safely heat your home or a contractor looking to provide your client with reliable heating solutions, Ingram's Water & Air can meet your needs. Ingram's Water & Air offers reliable, efficient and affordable home furnace systems to heat your home safely and effectively. Enjoy the colder months with warmth and peace of mind that your home's air is safe. Browse our wide selection of home furnace systems to save money and find the perfect heating system for your home.
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