leaking furnace when ac is on - Young's Home Comfort HVAC

Furnace Leaking Water when AC is On? Here’s Why!

How to fix a leaky furnace before it’s too late!

If you have a furnace leaking water, ignoring it can result in major problems and expenses. There are 2 main reasons why your furnace might leak water when the air conditioner is running. Although cleaning up the water from this leak can be easy, you will want to fix the root of the issue as soon as possible so you don’t end up with bigger and more expensive problems. Oftentimes, a water leak can cause damage that you can’t even see. So, consulting with a professional HVAC tech is highly recommended. Today, we will answer to this very important question of what to do when your furnace is leaking water.

Why is my furnace leaking water when the ac is on?

There are 5 main reasons your furnace will leak water when you run the air conditioner. Your air conditioner works by pulling water from humid air, and flowing it over the evaporating coils. This water drips into a chilling pan to be recycled back through your house as cold air. The remaining water from the pan is moved into the sewage line via your condensate drain. There are multiple parts or the air cooling process that can cause a leak. Some causes for leaks can be easily determined, while others need a deeper investigation. You can begin your assessment by using the list below. Then give our team of professionals a call to discuss your findings and set up a time to fix it!


Here are the 5 most common reasons your furnace is leaking water:


  1. Dirty Air Filter – Air filters should be changed regularly to keep sufficient air flow running through your unit. Insufficient or blocked air flow can cause your coils to freeze and then thaw back out once turned off. This creates excess water in your pan and might cause an overflow. Air filters should be changed typically every 1-6 months depending on where you live, pets and other household activities. 
  2. Clogged Condensate Drain – A clogged drain can cause the water to back up and leak out around the base of your unit. Clogs can occur when there is too much dirt, debris, rust or sludge in your drain pipe and not enough room for the water to properly drain out.  
  3. Disconnected Drain Line – It’s very rare that your condensate drain line will get disconnected. If your drain line does get disconnected, it is most likely a result of work done near the unit that knocked it loose. It can also occur over time or from improper installation. If you notice your furnace leaking, check to see if your drain is connected. If it is, turn off your unit and call a professional right away. 
  4. Condensate Pump – If your ac unit has a drain that is above it, then you will most likely have a condensate pump. Make sure that the pump is free of debris first before determining if it is functioning properly or not. 
  5. Bad Evaporator Coil – A damaged or broken evaporator coil can cause water to splash out instead of properly draining into the pan. Look for tiny drips instead of a puddle around the base of the furnace. Regular maintenance of your HVAC by a trusted professional will help prevent issues like this. 


How Serious is a Leaking Furnace?

While a leaking furnace is a common occurrence, ignoring it could cost you thousands to tens of thousands of dollars. Catching leaks early on helps you to avoid major structural damage to your home walls, flooring, ceiling and frame. Water leaks if not taken care of can also lead to mold growth which can lead to serious health hazards and ultimately decrease the value and safety of your home. 


Costly repairs to your HVAC and house may occur down the road if leaks if don’t get fixed. Smaller problems such as a dirty air filter can be fixed quickly and inexpensively. Make sure to do these at the first signs of a leak. If you ignore the signs from these initial problems, they can lead to problems in other parts of your HVAC system. Water from the leak can overflow off of the pan or around the furnace. This water can run into the floors, ceilings and walls, warping your drywall, wood and furniture permanently. 


Owning a home can be an expensive endeavor and we all try to save money where we can. Regular maintenance on your HVAC may seem like a hit to the wallet when everything is running smoothly, but you will be glad that you opted for it when you see how much more it can cost not to have it. Reach out to our team of specialists for more information on caring for your HVAC and implementing our preventative care services.

Home Care by Young’s

At Young’s, your home comfort is important. Water leaks can be somewhat of an inconvenience to fix if you haven’t stayed ahead of your service needs with regular HVAC maintenance. However, ignoring these small fixes can result in much more expensive and time consuming inconveniences later. A major HVAC replacement or repair can cost you tons of money and time, not to mention the damage done to your home that is potentially irreversible. Insurance will only cover issues if you are free from the responsibility of them. In other words, if you haven’t maintained your HVAC system, you might not get the help you need financially if something major breaks or is damaged because of it.

We want to provide you and your family a sense of home security. Give us a call today at (215) 234-4351 to schedule your HVAC check up and to get more information about our regular service and maintenance plans. You can also contact us on our website.