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How to Fix a Furnace Leaking Water

A puddle by your furnace is a sign that you need to learn how to fix a furnace leaking water. The water comes from condensation that occurs due to the heating process. The problem could come from broken drain lines, clogs, or a malfunctioning pump.

Tools NeededFurnace Leaking Water

  • A Flashlight
  • Wet/dry vacuum
  • PVC elbow and short length of pipe
  • Leak seal tape

Conventional and High-Efficiency Furnaces

The type of forced-air furnace you have determines how to inspect it for leaks. If a furnace still has its original Annual Fuel Utilization Efficiency label, look at the percentage printed on it. An 80% efficiency rating indicates a conventional furnace. An efficiency rating of 90% or higher proves that it is a high-efficiency furnace. In the absence of a label, look at the furnace’s exhaust system. A conventional furnace uses a metal exhaust pipe going into a chimney. A high-efficiency furnace has a plastic PVC pipe for an exhaust system.

How to Fix a Furnace Leaking Water Step by Step

Conventional furnace:

  1. Turn off the electrical power to the furnace for safety.
  2. Starting at the puddle, inspect the furnace for the source of the water leak.
  3. Look over the lines that connect the built-in humidifier with the drain line.
  4. If you spot a loose hose as the source of the leak, tighten the connection. If the leak persists, reach out to a furnace repair technician who can install new drain lines.
  5. If a line has a crack or pinhole, wrap it with leak seal tape. This is only a temporary fix. You still need to call a repair technician to replace the line.
  6. If you can’t find any leaks, the drain line could be clogged.
  7. At the top of the drain line, you should see a T-fitting with a screw cap on top.
  8. Unscrew the cap and pour distilled vinegar into the line.
  9. Vinegar can resolve small clogs. Otherwise, call for furnace repair.
  10. How to fix a furnace leaking water could require looking at the exhaust pipe.
  11. Do not touch the exhaust pipe. It could still be very hot.
  12. A loose connection at the furnace allows water vapor to condense on the pipe.
  13. If the leak is from a bad exhaust connection, call for professional repair. The furnace could also be leaking dangerous fumes into the house.

High-efficiency furnace:

  1. Turn off the electricity to the unit for safety.
  2. Locate the drain line coming out of the furnace.
  3. Inspect the connections for leaks.
  4. If you cannot find the source of the leak, the drain line could be clogged.
  5. Unscrew the cap on the top of the T fitting above the curved trap in the drain line.
  6. Pour distilled vinegar into the line.
  7. If vinegar fails to dissolve the clog, disconnect the lower line from the condensate pump.
  8. Build an adapter for a wet/dry vacuum.
  9. Use a PVC elbow and a short length of PVC pipe to make the adapter.
  10. Put the adapter between the vacuum hose and the line beneath the trap.
  11. Run the vacuum to suck out the clog.
  12. Pour water into the top of the line and vacuum the line repeatedly until it flows smoothly.
  13. Reconnect the pump and screw the cap back on the T.
  14. If a clog is not the problem, the condensate pump could be broken. Hire a furnace technician to install a new one.

Furnace leaking when the air conditioner runs:

  1. Turn off the power supply to the heating and cooling system.
  2. Look near the top of the furnace to find the drain lines for the AC system.
  3. Inspect the connections or look for clogs.
  4. Repair bad connections or suck out a clog with a wet/dry vacuum.

Experienced Heating Repair Technicians at Your Service

Licensed furnace repair specialists at Oliver are trained to fix any type of furnace water leak. Don’t let moisture put your home at risk of mold. Contact us online or call us today at 1-888-810-2681 for trusted furnace repair.

Need help with this project?

If you do not have the time, tools, or experience necessary to complete the project, please contact the professionals at Oliver for help.

Contact us today at 1-888-810-2681 Get a Free Estimate
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