Fix it
Why is my AC leaking water?
An air conditioner makes water by design — gallons of it on a humid day — and a leak indoors means that condensate is not making it out. The plumbing is simple, which is why this is one of the most fixable problems on the list.
What it usually is
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A clogged condensate drain line
Algae and dust jelly up the drain over a season or two; water backs up the pan and over the edge. Far and away the most common cause, and the most preventable.
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A rusted-through or cracked drip pan
Primary pans on older units corrode. Water appears under the air handler even when the drain runs clear.
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A frozen evaporator coil thawing between cycles
A coil iced by weak airflow or low charge melts when the compressor stops, releasing more water than the pan handles. If the leak follows periods of poor cooling, suspect ice.
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A failed condensate pump on below-grade installs
Where gravity cannot drain, a small pump lifts the water out; when it dies, the reservoir simply overflows.
What you can check yourself
Kill power to the unit at the switch. Find the drain line (PVC leaving the indoor coil) and clear it — wet/dry vacuum suction at the outdoor termination works well. Flush a cup of diluted vinegar down the line access to slow regrowth. Check the pan for rust and the coil for ice.
When it’s a job for a pro
Recurring clogs justify re-pitching or enlarging the drain; a rusted pan or frozen coil is a service visit — ice especially, because its cause (airflow or charge) is the real problem.
A drain clearing typically runs $100 to $250; pan replacement $250 to $600; a condensate pump $150 to $350 installed.
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