Why Is Furnace Leaking Water? Common Causes & Solutions

Why Is Furnace Leaking Water?

A furnace can leak water due to various reasons.

In a high-efficiency condensing furnace, the issue may be caused by clogged condensate drains or a malfunctioning condensate pump.

Clearing the drain with hot water and vinegar can help, and annual inspection and cleaning should be done.

Replacing a condensate pump can cost between $100 to $200.

For a conventional furnace, water leaks can be caused by a clogged humidifier drain line or an ill-fitted exhaust pipe.

Checking the humidifier water lines and exhaust pipe fit is recommended.

If the air conditioner is running, water can accumulate if the condensate drain line is clogged or if there’s a leak in the drain pan.

If the leak is not from the AC drain line and the AC hasn’t operated lately, it is recommended to call an HVAC professional for help.

Furnace leaks can often be repaired at a lower cost than replacing the entire unit, with an average cost of $300 for repairs and $4500 for replacement.

If the furnace is old, has had recent repairs/upgrades, energy bills are increasing, or strange noises are present, it may be time to consider replacing the entire system.

Professional assistance is important, and when choosing a furnace repair company, it’s advisable to read online reviews, ask for a written quote, and get estimates from multiple companies.

Access to a furnace troubleshooting guide is also important to identify other potential issues.

Key Points:

  • A furnace can leak water due to various reasons, including:
  • Clogged condensate drains
  • Malfunctioning condensate pump in a high-efficiency condensing furnace
  • Clearing the drain with hot water and vinegar can help, and annual inspection and cleaning should be done.
  • Replacing a condensate pump can cost between $100 to $200.
  • For a conventional furnace, water leaks can be caused by:
  • Clogged humidifier drain line
  • Ill-fitted exhaust pipe
  • Checking the humidifier water lines and exhaust pipe fit is recommended.
  • If the air conditioner is running, water can accumulate if:
  • The condensate drain line is clogged
  • There’s a leak in the drain pan
  • If the leak is not from the AC drain line and the AC hasn’t operated lately, it is recommended to call an HVAC professional for help.
  • Furnace leaks can often be repaired at a lower cost than replacing the entire unit, with an average cost of $300 for repairs and $4500 for replacement.
  • Professional assistance is important, and when choosing a furnace repair company, it’s advisable to:
  • Read online reviews
  • Ask for a written quote
  • Get estimates from multiple companies
  • Access to a furnace troubleshooting guide is also important to identify other potential issues.

Did You Know?

1. The furnace is not actually leaking water, but rather it is producing condensation. As the warm air from the furnace meets the cold air outside, condensation forms on the surfaces of the furnace and pipes, creating the appearance of a leak.

2. One possible reason for excessive condensation in the furnace is a clogged condensate line. Over time, debris, mold, or algae can accumulate in the line, hindering the proper drainage of condensation. Regular maintenance and cleaning of the line can prevent this issue.

3. When a furnace is installed in a basement, the condensation produced can be used as a resource. Some homeowners utilize a condensate pump to collect and redirect the condensation from the furnace into their household plumbing system, effectively using it as a water source for other purposes.

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4. In extremely cold weather conditions, the moisture in the exhaust gases from the furnace can freeze and block the furnace’s exhaust pipes, resulting in the backup of condensation. To prevent this, some furnaces are equipped with special devices called condensate traps, which collect and drain the condensed water before it can freeze.

5. Excessive humidity levels in a home can increase the amount of condensation produced by a furnace. To mitigate this, homeowners can use a dehumidifier to regulate indoor humidity levels, thus reducing the amount of condensation created by the furnace.

Types Of Furnaces: High-Efficiency Vs Conventional

There are two primary types of furnaces commonly found in residential homes: high-efficiency condensing furnaces and conventional furnaces. Understanding the differences between these two types is essential when it comes to troubleshooting and addressing issues such as a furnace leaking water.

High-efficiency condensing furnaces are designed to maximize energy efficiency and minimize waste. These furnaces achieve higher levels of efficiency by extracting heat from the combustion gases before they are vented out. This process results in cooler exhaust gases that can be vented through a PVC pipe, which is commonly used for intake and exhaust purposes.

On the other hand, conventional furnaces have a simpler design and lower efficiency ratings compared to their high-efficiency counterparts. These furnaces typically have an 80% Annual Fuel Utilization Efficiency (AFUE) rating. The exhaust gases produced in conventional furnaces are vented through a metal pipe, which differs from the PVC pipe used in high-efficiency furnaces.

Determining Furnace Type: Exhaust Pipe And AFUE Rating

To determine the type of furnace you have, there are a few indicators to look for:

  1. Exhaust Pipe Material: Check the material of the furnace exhaust pipe. If it is made of PVC, it indicates that you have a high-efficiency condensing furnace. On the other hand, if the exhaust pipe is made of metal, it suggests that you have a conventional furnace.

  2. Annual Fuel Utilization Efficiency (AFUE) Rating: Look for the AFUE rating to further determine the furnace type. High-efficiency furnaces typically have a higher AFUE rating, often exceeding 90%. In contrast, conventional furnaces typically have an AFUE rating of around 80%. The AFUE rating represents the percentage of energy that is converted into usable heat for your home.

Identifying your furnace type is especially useful when troubleshooting a furnace leaking water. Different types of furnaces may have distinct issues. By understanding the type of furnace you have, you can choose the appropriate solution or ask relevant questions when consulting a repair technician.

  • This can be helpful in identifying potential causes for furnace leaks.
  • Different furnace types may have distinct issues.
  • Understanding your furnace type can guide you in choosing the appropriate solution or asking the right questions when consulting a repair technician.

Common Causes Of Leaks In High-Efficiency Furnaces

High-efficiency condensing furnaces can experience water leaks due to various reasons. One common cause is clogged condensate drains. These drains are responsible for removing moisture and condensate produced during the combustion process. Over time, these drains can become clogged, leading to water leaks.

A malfunctioning condensate pump can also contribute to water leaks in high-efficiency furnaces. The condensate pump is responsible for moving the water from the drain to an appropriate location, such as a floor drain or an outside area. If the pump fails to function correctly, it may result in water accumulation and subsequent leaking.

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To address these issues, clearing the clogged condensate drains can be done by using a mixture of hot water and vinegar. However, it is important to turn off the furnace before attempting any maintenance or repairs. It is also recommended to have your high-efficiency condensing furnace inspected and cleaned annually to prevent potential leaks.

In some cases, replacing a malfunctioning condensate pump may be necessary. The cost of replacing a condensate pump can range from $100 to $200, depending on the specific model and any additional labor costs that may be associated with the replacement. Consulting with a professional HVAC technician is advisable to ensure proper diagnosis and resolution of the issue.

Common Causes Of Leaks In Conventional Furnaces

Water leaks in furnaces can be attributed to different factors depending on the type of furnace. In conventional furnaces, one common cause of leaks is a clogged drain line for the humidifier. The humidifier adds moisture to the air, and if the drain line is obstructed, excess moisture can accumulate and cause water leakage.

Another possible cause of leaks in conventional furnaces is an ill-fitted exhaust pipe. If the exhaust pipe is not properly aligned or sealed, it can allow water to escape and create leakage issues. Checking the humidifier water lines and ensuring the proper fit of the exhaust pipe can help address these potential sources of leaks.

It is important to note that when the air conditioner is running, it dehumidifies the air and releases the moisture through the condensate drain line. If the drain line is clogged or there is a leak in the drain pan, water can accumulate on the ground. This can sometimes cause confusion about why the furnace is leaking water, especially when the AC drain line is located near or on top of the furnace.

If the AC has not been used recently and the furnace is still leaking water, it is advisable to contact an HVAC professional for assistance. They can help identify and resolve the issue, ensuring that your furnace operates efficiently without leaks.

Repairing Vs Replacing A Leaking Furnace

When facing a leaking furnace, it is important to weigh the options of repairing versus replacing the unit. In many cases, furnace leaks can be repaired at a lower cost than completely replacing the entire unit. The average cost of furnace repairs is around $300, depending on the specific issue and the required parts or labor.

However, there are instances where it may be more practical to replace the entire furnace system. Factors to consider when deciding on replacement include:

  • The age of the furnace
  • Recent repairs or upgrades
  • Escalating energy bills
  • Unusual noises or performance issues

If your furnace is 16 years old or older and exhibits these warning signs, it may be a good time to consider replacing the entire system.

It is crucial not to ignore the warning signs of a failing furnace and to replace it while it is still operable. A malfunctioning furnace can pose safety risks and result in costly repairs or higher energy bills. Seeking professional advice from HVAC technicians can help determine the best course of action for your specific situation.

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When hiring a furnace repair company, it is recommended to:

  1. Read online reviews
  2. Ask for a written quote
  3. Obtain estimates from at least three companies
  4. Requesting a copy of the company’s warranty for parts and labor is also important to ensure that you are covered in the event of future issues.

Although furnaces typically have a lifespan of 16 to 20 years, having access to professional assistance is crucial in maintaining their optimal performance. Regular maintenance, inspections, and troubleshooting can help prolong the lifespan of your furnace while ensuring the comfort and safety of your home.

If the issue is not related to a leaking furnace, consulting a furnace troubleshooting guide can help identify other potential problems with your unit.


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Frequently Asked Questions

How do I stop my furnace from leaking water?

To prevent your furnace from leaking water, you can start by shutting off the system. Locate the shutoff switch, typically found next to the furnace and coil, and turn it off. Once you’ve eliminated the power source, it’s crucial to clean up the water quickly to avoid any further damage. Additionally, check the filter to ensure it’s not clogged, as a dirty filter can lead to water leakage. Another method involves placing a vacuum around the PVC drain line to remove any blockages that may be causing the leakage. Lastly, pouring water into the top of the condensate pump can help flush out any debris and improve its functionality, preventing water from accumulating and leaking.

Where does a furnace leak water from?

A furnace can leak water from the condensate pump or a blocked drain. If the condensate is not draining properly and water is found on the floor around the furnace or rust stains are present within the cabinet, a blocked drain may be the culprit. Additionally, a malfunctioning pump can cause water to flow back and lead to a leak.

Is a furnace leaking water an emergency?

Although a furnace leaking water doesn’t necessarily classify as an emergency, it is still crucial to address the issue promptly. The presence of water may indicate a potential fault or impending breakdown in the furnace system. Therefore, it is recommended to contact a technician to inspect and address the problem to avoid further complications. While waiting for the technician, it is advisable to clean up the water to minimize any potential damage.

Why is furnace leaking water in summer?

A possible reason why a furnace may be leaking water in the summer is due to a shared internal drain with the AC unit. If the drain becomes blocked with dirt and dust, the condensation produced by the HVAC system can overflow and leak onto the floor underneath the furnace. This can occur when the AC unit is running often in the summer, exacerbating the issue of a clogged drain. It is important to regularly clean and maintain the drain to prevent such leaks and ensure proper functionality of both the AC and furnace systems.

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