Can Water Damage a Furnace?

Excessive water presents a risk to every aspect of your home, from the structural elements to the personal belongings to the air you breathe. And nowhere is the water damage risk greater than to the systems that keep your family comfortable and safe, such as your furnace. 

Not only can water damage your home’s furnace — it can cause lingering problems that put you and your family at risk long after the initial event took place. This includes damage to the furnace components themselves, surrounding areas of your home, pipes, and insulation connected to your furnace, and even the air inside your home that your furnace is heating.

If you’ve experienced a recent weather catastrophe, plumbing failure, or other event that brought large amounts of water into your home, do not overlook the potential damage to your furnace. Particularly for homes with furnaces located in the basement, the risk of these water events can be significant.

From making a home unlivable to actually posing a physical risk to your family, keep reading to find out why water damage to your furnace poses such a big risk. 

Hurricanes, flash floods, and catastrophic plumbing failures present an obvious threat to your home heating system. However, water damage events sometimes aren’t as obvious. From localized flooding to a slow leak to a backed-up drain, relatively minor water risks can still lead to significant damage to your home’s heating system. The key is to know how to spot these subtle clues of potential furnace damage:

• Puddles and wet spots on the floor or near your furnace
• Dirt, silt, and other foreign substances near your furnace
• Mold and mildew growth around your furnace
• Furnace reliability issues and malfunctioning
• A rotten egg odor indicating a gas leak in your natural gas furnace

If you notice any of these warning signs of damage, don’t tackle the repairs yourself. When dealing with gas or fuel oil systems, get a second opinion from a respected company that specializes in these remediation services. 

The Pennsylvania Department of Environmental Protection notes that even if it’s not visually apparent, significant water damage could have occurred to your furnace after an unexpected water event. The valves and controls can begin experiencing corrosion from water that got inside, even if the exterior is totally dry. This can lead to a number of serious risks, including poor furnace performance, fire, and even explosions if it’s started without undergoing repairs. 

Even if you flip on your furnace and it appears to be working fine after a flood or water intrusion, it may not last. Parts that were exposed to water may eventually "corrode and malfunction," even if they’re fine today. Your warranty coverage may too disappear, leaving you with a big surprise bill when the unit dies prematurely. 

It’s not just the furnace unit itself that is at risk for water damage. The ductwork and insulation surrounding this unit that helps to move the heated air can also experience significant issues in the event of unexpected water exposure. In some cases, the damage may be as bad as the impact on the furnace itself.



FEMA notes that air registers and diffusers should be taken out, cleaned, and disinfected after a flooding event. As for air ducts and ductwork, it’s nearly impossible to fully clean lined ductwork that was exposed to water. The only type of ductwork that can be salvaged is unlined sheet-metal ducts that won’t harbor water and can be fully sanitized.

The CDC explains that you should always have your HVAC system professionally checked and cleaned after a flood or unexpected water event. This professional should be experienced in moisture and mildew cleanup. Wet ductwork offers an ideal mold growth environment. Prematurely starting your furnace after a water event, even if it appears to be operating properly, can pose a serious health risk by spreading unwanted growth throughout your home’s air.

A professional company can verify your system is working properly, kill the mold and mildew, and prevent a later growth that could continue to pose a health risk. Only after this professional inspection should you use your home’s furnace. As an invisible threat, mold and mildew pose a hidden risk that can lead to several serious health consequences.

Few things are as devastating to homeowners than a flood, plumbing issue, roof leak, or other unexpected water event. You and your family will likely lose valuable personal belongings and your home may have to undergo significant restoration and repairs, depending on the extent of the damage. Worst of all, this event can create many long-term problems that you may be dealing with for years to come. 

Although you can’t prevent all instances of furnace damage due to water exposure, you can take some steps to mitigate the risks. HGTV recommends raising your furnace if you live in a flood-prone area. In some cases, that may be as simple as using concrete blocks or other materials to elevate it if water doesn’t generally get much more than a few inches deep.

If you live in an area with major flood risks, you might consider moving it up a level from your basement or lower level of your home to a higher level or even an attic. If none of these options is possible, you can also construct a flood wall around your unit to help mitigate the flood risks.

If sewer backups are an issue, install back-flow valves to prevent backup through your drain pipes. You can also take steps to prevent water from making it into your home altogether. This includes landscaping changes that direct water away from the base of your home. You can also consider applying a waterproof veneer to the exterior walls of your home.

If your home or neighborhood experienced some unexpected flooding, plumbing leak, or other water-related event, don’t ignore it. Take the time to evaluate your furnace system and look for any of the warning signs. You don’t need to know why your furnace is malfunctioning, but you do need to bring in a professional company that specializes in identifying and solving water damage issues. The risks to you, your family, and your home are just too great to overlook.