A nice puddle to jump in after a rain shower leaves you with a fun, happy feeling. Finding a puddle of water that has leaked from your furnace – not so much. A furnace water leak doesn’t usually mean a huge repair bill, so don’t worry just yet!

The most common reason for a furnace to leak water is a condensation leak. You will need an HVAC service professional to visually inspect and test the unit in order to diagnose this with certainty, but here is some information to give you a little insight into if you may have this type of leak. The likelihood that you have a condensation leak really depends on the type of furnace you have. High-efficiency furnaces (95%+ AFUE) will be more likely to leak water due to condensation because they extract heat from the combustion gases for a longer period of time when compared to standard-efficiency furnaces. Standard efficiency furnaces (80% AFUE) vent this water out an exhaust or flue pipe. In high-efficiency systems, however, this condensation is routed to a floor drain. Here is where a few issues may arise.

If you do have a condensation leak and a high efficiency furnace, you might have:

  1. A clogged condensation drain
  2. A break in the condensation line
  3. Issues with the condensate pump

If you have a standard efficiency system it is still possible that you have this type of leak, but would most likely be due to the exhaust or flue pipe being incorrectly sized.

If your HVAC service expert determines that you do not have a condensation leak, there are a myriad of other issues that could be the cause of your furnace leaking water. They include

  1. Issues with your whole-house humidifier (if you have one)
  2. Internal drain clog
  3. Bad secondary heat exchanger in the furnace – the most expensive to repair and may need replaced entirely
  4. Air conditioner leaking

Air conditioner leaking, you say? Yes, in seasons where you may use the furnace and air conditioner it is possible that when you are using the AC your condensation pan can fill with water and drip into your heating system, making you think you have a furnace leak problem.


First, call a professional HVAC service company. You’ll want to tell them about your issue and get on the schedule as quickly as possible.

Then, make sure you shut your system off. There should be a switch next to the furnace. If you cannot locate this switch, then turn the system off at the breaker box.

Clean up all the water as best as you can. Water damage can happen quickly and this will also allow the technician to get access to the unit more quickly when he or she arrives.


Call us at Quality Comfort Heating & Cooling at 513-216-0586 if you are experiencing a furnace leak or are in need of any other furnace repair. You can also book online at our website myqualitycomfort.com. Our trained and certified technicians come with fully stocked vehicles, ready to fix your furnace problem. We also provide a lifetime guarantee on our repairs.