How to check your AC condensate drain
Updated . By the OakTend team.
As it cools, your AC pulls water out of the air. A condensate drain line carries that water from a pan under the indoor coil to the outside or a drain. Algae and dirt can plug it.
Why it matters
A plugged drain can cause water damage inside the house and raise indoor humidity, and it can breed bacteria and mold, according to ENERGY STAR. In homes with the air handler in the attic, an overflow shows up as a ceiling stain.
Steps
- Turn the AC off at the thermostat.
- Find the drain line at the indoor unit and follow it to where it ends outside or at a drain.
- Look at the pan under the coil, if you can reach it, for standing water, and check nearby for stains.
- Clear a clog at the outside end with a stiff wire, or by holding a wet and dry vacuum hose over the end.
- Turn the AC back on and, after a while, confirm water drips steadily from the end of the line.
When to call a pro
If the pan keeps filling, water drips from the unit or the ceiling, or the line plugs again soon after you clear it, have an HVAC technician clean and test the drain and any overflow switch.
Safety
Turn the system off before working near the indoor unit, and be careful on attic joists: step only on framing, never on the ceiling drywall between them.
Go deeper
General information, not professional advice. Your equipment's manual comes first when it says something different.
Sources
- ENERGY STAR: heating and cooling maintenance checklist
Check and inspect the condensate drain on a central AC, furnace or heat pump in cooling mode. - ENERGY STAR: a guide to energy-efficient heating and cooling
A plugged drain can cause water damage, affect indoor humidity and breed bacteria and mold. - U.S. Department of Energy: Energy Saver 101, home cooling
Pass a stiff wire through the unit's drain channels occasionally to prevent clogs.