DIY guideFurnace
Clear the condensate drain and trap
Flush the small drain line that carries water from the AC coil or a high-efficiency furnace, so it can't back up, shut the system down or flood the floor.
- 15 to 30 min
- 8 steps
- Every step animated
8 steps
Tap a step to watch it again.
Set the thermostat to Off, then turn off the switch on or beside the unit.
If the switch or the floor around it is wet, turn off its breaker from a dry spot instead.Follow the small white pipe or clear hose from the unit down to a floor drain or a small pump.
Near the unit, the pipe has a T with a cap or a plug on top. Pull it off.
Pour a cup of warm water, or white vinegar, into the T. Watch it run out at the drain or into the pump.
If the pipe has a U-shaped trap outside the cabinet, unscrew it, rinse out the slime and screw it back hand-tight. One inside the cabinet is a pro's.
If the unit sits over a drip pan, look in it. It should be dry; standing water means the line is still blocked.
Put the cap back, turn the unit's switch on and set the thermostat. Water should drip out at the drain end as it runs.
If the water won't run through, or the pan keeps filling, switch the unit off and ask Handyman for a heating and cooling tech.
What you need
- A cup of warm water or white vinegar
- A small funnel
- A bucket and a towel
- A flashlight
Call a pro if
- Water won't run through the line
- The drip pan keeps filling, or water drips from the unit
- The trap is inside the cabinet
- The pump hums but doesn't empty
Handyman says: Still blocked? I'll find an HVAC tech.
Free for every home. Handyman asks a few questions, then books a pro it trusts.
More heating and air guides
See all 51
Rather have
a pro do it?