AC leaking water inside? What to check first
Quick answer
An AC leaking water indoors is almost always a clogged condensate drain line backing up, a full or cracked drain pan, or a frozen evaporator coil that's melting. First, turn the system off to stop the water and protect your ceiling and floors. Then replace a dirty filter (a common cause of coil freezing) and clear the condensate drain line — a wet/dry vac on the outdoor end usually does it. Persistent leaks or a frozen coil that keeps coming back need a pro.
Common causes
- A clogged condensate drain line (algae and sludge) backing water up into the unit.
- A full, rusted, or cracked drain pan.
- A frozen evaporator coil — from a dirty filter or low refrigerant — that melts and overflows.
- A disconnected or improperly sloped drain line.
- A failed condensate pump on attic or basement units, or extreme humidity overwhelming the drain.
What to check first
- Turn the AC off to stop more water and limit damage.
- Replace a dirty air filter — restricted airflow is a top cause of a frozen, then dripping, coil.
- Check for ice on the coil or refrigerant line; if frozen, let it thaw fully before running again.
- Clear the condensate drain line — use a wet/dry vac at the outdoor drain outlet, or flush it.
- If your unit has a condensate pump, check that it's running and not clogged.
When it's urgent
Water around the air handler can damage ceilings, drywall, and flooring, and reach electrical components — turn the system off and dry the area. An attic unit is especially urgent because a leak shows up as a ceiling stain below. A safety float switch should shut the system down when the pan fills, but don't count on it.
DIY vs. call a pro
You can likely DIY
- Turning the system off and replacing the filter.
- Clearing the condensate drain line.
- Emptying or unclogging a condensate pump.
Call a pro for
- A coil that keeps freezing (often a refrigerant problem).
- A cracked or rusted drain pan, or a failed condensate pump.
- Persistent leaks after the drain line is clear.
Estimated cost range
How HouseCue helps
HouseCue is a private, homeowner-first app that turns this from a one-time worry into a tracked plan. Snap a photo for an AI diagnosis, upload your inspection report to auto-build a handbook, and get seasonal reminders for your roof, HVAC, water heater, plumbing, and electrical — so nothing slips. Connecting with a pro is always optional and only when you choose.
Get started freeFrequently asked questions
Why is my AC leaking water inside the house?
Usually a clogged condensate drain line that's backing up, a full or cracked drain pan, or a frozen coil that's melting. Turn the system off, replace a dirty filter, and clear the condensate line; if it keeps happening, have a technician check for a refrigerant or pan problem.
Is an AC water leak an emergency?
It's not dangerous like a gas leak, but it can cause real water damage to ceilings, walls, and floors — especially from an attic unit — and water near electrical parts is a concern. Shut the system off and dry the area, then address the cause.
How do I clear a clogged AC condensate line?
Find the drain line's outdoor outlet (a PVC pipe near the outdoor unit) and use a wet/dry vacuum to pull the clog out, or flush the line. Many units also have an access port near the indoor coil. If it clogs repeatedly, ask a pro about adding a cleanout and treatment tablets.
Related guides
HouseCue guides are general educational information, not professional inspection, engineering, or contracting advice. Costs vary by market. For safety issues — gas, electrical, structural, or major water — contact a qualified professional.