AC Leaking Water Inside the House? Causes and Fixes
Water is dripping from the indoor unit, staining the ceiling, or pooling around the air handler.
Likely causes
| Cause | Likelihood | Typical cost |
|---|---|---|
| Clogged condensate drain line | 55% of calls | $185 – $245 |
| Frozen evaporator coil thawing | 20% | $185 – $695 |
| Rusted or cracked drain pan | 10% | $385 – $795 |
| Disconnected or sloped-wrong drain line | 8% | $225 – $445 |
| Dirty filter restricting airflow | 5% | $20 filter |
| Failed condensate pump | 2% | $285 – $495 |
Safe DIY checks (do these first)
- 1
Shut the system off
Turn the thermostat to OFF at the first sign of water. Continuing to run it keeps producing condensate and risks drywall and ceiling damage.
- 2
Soak up standing water
Clear the pan and floor so you can tell whether the leak is continuing or was a one-time overflow.
- 3
Check the air filter
A clogged filter freezes the coil, and the melt overwhelms the pan. Replace it if it is gray or matted.
- 4
Find the outdoor drain stub
Look for a small PVC pipe near the condenser or on an exterior wall. If nothing drips from it while the system runs, the line is clogged.
- 5
Try a wet/dry vacuum
Seal a shop vac to the outdoor drain stub for two minutes. This clears many simple algae clogs. If water still does not flow, call.
When to stop and call a pro
- • Water is staining a ceiling or wall
- • The drain line is still blocked after vacuuming
- • Ice is visible on the copper lines or the indoor coil
- • The drain pan is rusted through or cracked
- • The leak returns within days of clearing
Typical repair cost
$185 – $795. Drain clearing with a safety-switch test is $185 to $245; replacing a rusted secondary pan or repairing the coil runs $385 to $795.
Frequently asked questions
Why is my AC leaking water inside the house?
About 55 percent of the time it is a clogged condensate drain line — algae and dust build a plug, the pan overflows, and water finds the ceiling. The next most common causes are a frozen evaporator coil thawing faster than the pan can drain, and a rusted-through drain pan.
Is an AC water leak an emergency?
It is urgent. Shut the system off immediately — the equipment is not in danger but your drywall, insulation and framing are, and a slow leak into a ceiling cavity turns into a mold problem within days.
Can I fix an AC water leak myself?
You can attempt the simple version: change the filter, and use a wet/dry vacuum on the outdoor condensate stub for a couple of minutes. If water does not begin flowing freely, the clog is deeper or the pan is compromised and needs a technician.
How much does it cost to fix an AC leaking water?
$185 to $245 for a professional drain clear including a float-switch test and a biocide tablet. Pan replacement runs $385 to $795, and a coil-related leak repair with recharge is $295 to $695.
Why is my AC leaking water only at night or in the morning?
That pattern points to a partially frozen coil. The system ices during long runtimes, then thaws when it cycles off, dumping more water than the pan can handle. The underlying cause is low refrigerant or restricted airflow.
How do I prevent AC drain clogs?
Change filters on schedule, have the drain flushed and treated at every annual tune-up, and keep a condensate tablet in the pan. In desert climates dust load makes drain maintenance more important than in coastal homes.
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