Why Is My Furnace Leaking Water When the AC Is On?

Noticing any water pooling inside your home is never a good sign, but a leaking furnace can be a cause for extra concern.  Pooling water or excessive condensation can cause any number of problems including mold and mildew which can cause allergies or production of rust damage!  An excess of water can also cause your HVAC system to break down long before it’s supposed to, so it’s important to address as soon as possible.

What exactly causes this leak?  In this article, we help you understand some possible causes of this leak before you call in the professionals.  The visualization of the leak coming from your furnace is in most (if not all) cases caused by the fact that the drain pipe for your AC unit is the same drain pipe that your furnace uses.  This causes the furnace to leak when there is a problem with the AC unit.


Always Turn Off Your HVAC

First thing’s first, however.  If you notice water leaking the first thing you’re going to want to do is turn off your HVAC system.  This can be done either by finding the off switch, but if this is blocked or difficult you can turn it off at the fuse box.  If you have access to a Wet Vac (a vacuum that can suck up water), use it to clean up any standing water.  Standing water can cause damage to your floor/carpeting, or worse cause an electrical fire by coming into contact with an outlet.

  • Drain Line Not Flush: The best-case scenario and the easiest solution is that your drain pipe simply got knocked loose.  Check to make sure that it is lined up with the output from your unit.  If it’s loose, realign it and check to make sure that it is tightly sealed.
  • Clogged Drain: Your AC unit is going to produce some condensation, especially on those hot and humid NYC days.  This condensation typically is removed through a drain pipe to prevent pooling, however, if this drain becomes clogged, it can cause the water to back and eventually leak!  If the cause is a clogged drain, there are a few ways you can go about cleaning it.  One way to clean it is to use a wet vac to suck out any debris that may be present in the pipe.  Another option is to use compressed air to push the clog out.  Lastly, you can buy drain cleaning tablets that are available at most grocery or hardware stores that can help get the job done.
  • Evaporator Coil: The evaporator coil works very similarly to air conditioning ducts in that it takes air in and then cools and dehumidifies it through a series of coils.  As the air is dehumidified this produces a condensation which can drip into a pan which in turn is drained.  If your evaporator coil is not functioning properly this could cause an excess of water production or several other issues, which could be causing your furnace to leak.
  • Cracked Drain Pan: As mentioned above, when the evaporator coil is working properly the condensation that is produced is dripped into a pan that drains out of the pipe.  If this pan is cracked the water will simply drip down the inside of your unit, causing a leak!


Still Need Help?  Call Figlia & Sons!

If your furnace has been leaking for a long time or if you are not sure when it started, it is best to get someone to conduct an inspection because parts may be corroded or severely damaged by water, putting your HVAC system at risk for more expensive repairs.

For your New York City HVAC needs, contact the experts at Figlia & Sons to solve the problem efficiently and quickly. With over 50 years of experience in the installation, repair, and replacement of HVAC equipment our highly skilled technicians will provide fast and reliable service to your unit. Call us today at 917-979-5731 to speak with a knowledgeable representative from our team!

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