My Gas Furnace Is Leaking Water Into the Drip Pan


If your gas furnace is leaking water into the drip pan, you need to find out where the problem is coming from as soon as you can, or you could end up with some expensive repairs. If the water is running out of the drip pan and down through the inside of your furnace, it could damage the heat exchanger, the blower fan or other electrical components.

Evaporator Coil

  • An up flow gas furnace with an integrated air conditioner usually has an evaporator coil placed on top of the furnace for the air conditioning part of the system. Sometimes, the evaporator coil freezes up and ice forms on the coil. When the air conditioner cycles on and off, the ice melts and may overflow the drain pan, causing the water to run down inside the furnace.


  • Some drain pans are made out of metal. If the drain pan has a hole in it, the water in the pan will drip on the furnace. You should also check the drain hose for holes and replace it if necessary. According to Air Comfort Systems, you should replace a bad hose with black hose instead of clear hose because the clear house works like a greenhouse to encourage the growth of algae. Cracked fittings can also cause leaks. Check fittings at elbows, couplers and drain pan.

Clogged Line

  • The drain pan can also overflow if the drain lines are plugged. Use a shop vac to suck up whatever is clogging the line. You can also squeeze the hose with your fingers to loosen up a dirt clog, or use a pipe cleaner to clean the plug, after detaching the hose from the fittings. If a lot of water leaked down into your furnace, you’ll need to call an HVAC technician to check the furnace’s electrical components for water damage. Adding an inline drain switch will ensure that the system is turned off before water leaks into the furnace. A secondary drain line will keep everything draining properly if the main line becomes clogged.

Hose Problems

  • Some problems are easy to fix yourself. An air lock in the drain hose occurs when the hose is underwater and an air bubble forms inside the hose. The water in the drain seals the hose so no water can drain out. Pick the hose up out of the water and cut off the end to shorten it. A crushed hose can also cause water to back up and leak. Check to make sure nothing is sitting on top of the hose. Finally, make sure the hose from the furnace to the drain runs downhill and that there are no kinks in it.

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