AC problem guide

Water Leaking From Your AC or Around the Air Handler?

A puddle under the indoor unit is usually drainage, not refrigerant — but it can soak drywall fast. See the likely causes and how urgent yours is.

Check My AC Problem Read the Guide

Shut It Down and Call a Pro If You See This

Treat it as urgent if you see:

Water near electrical panels, disconnects, or the air handler wiring
A ceiling below an attic unit that is stained, sagging, or dripping
Standing water that keeps returning after you mop it up
A burning or electrical smell from the unit
Visible ice on the coil or refrigerant lines

Water plus electricity is the part to take seriously. If the leak is near wiring, the disconnect, or a ceiling below an attic unit, turn the system off at the thermostat and the breaker, then get a technician out before the drywall gives.

Quick answer

Start by turning the system off so the coil stops making condensate. Then check the air filter and the condensate drain line — a clogged drain is by far the most common cause of an indoor AC leak. If you see ice on the coil, let it thaw with the fan running before anyone inspects it. Persistent or repeat leaks usually mean a failed pan, pump, or float switch, and those are service calls. This page is educational information, not a diagnosis of your system.

Possible causes

Clogged condensate drain line

Algae and dust plug the drain, so condensate backs up into the pan and overflows. This is the single most common cause.

Cracked or rusted drain pan

Older pans corrode through and drip even when the line is clear.

Frozen evaporator coil

A dirty filter or low refrigerant ices the coil; when it thaws, the pan cannot keep up with the meltwater.

Failed condensate pump

Attic and basement units pump water uphill. When the pump dies, the pan overflows within hours.

Disconnected or sloped-wrong drain

A line that came loose at a joint or lost its downhill pitch dumps water inside the cabinet.

Dirty air filter

Restricted airflow drops coil temperature below freezing and starts the freeze-and-thaw cycle.

Poor insulation on refrigerant lines

Bare suction lines sweat heavily in humid weather and mimic a leak.

Low refrigerant

A charge loss both freezes the coil and points to a refrigerant leak that needs a licensed tech.

How this project is usually classified

General guidance for this problem type — not a diagnosis of your home.

Typical urgency: Urgent — within days
Safety risk: Moderate safety risk
DIY suitability: Pro recommended
Cost level: Moderate cost
Repair option: Capacitor, contactor, or leak repair on a system with remaining service life.
Replacement option: Replacement when the compressor fails or the system uses obsolete refrigerant.
Typical timeline: Same-day diagnosis in season; replacement 1–2 days
Contractor type: hvac

What you can safely check yourself

Turn the system to OFF at the thermostat so the coil stops producing condensate.
Check and replace the air filter if it is gray or matted.
Look for standing water in the drain pan and follow the drain line to the outside exit point.
Check the float switch — many units shut off automatically when the pan fills.
Photograph the puddle, any ceiling staining, and the drain line before you clean up.

Before the pro arrives

• Know the system age, brand, and where the indoor unit sits (attic, closet, basement).
• Note whether the coil looked frozen and how long the leak has been happening.
• Have photos of the pan, drain line, and any water damage.
• Mention your last maintenance visit, if any.

Questions to ask

• Is this a drainage problem or a refrigerant problem?
• Did you test the float switch and clear the full drain run?
• Is the pan repairable or does it need replacement?
• What maintenance prevents this from recurring next season?
• Is any water damage above the ceiling that I should have inspected?

Common questions

Is a leaking AC dangerous?

The water itself is condensate, not refrigerant, so it is not toxic. The risk is water damage and electrical hazard: an attic unit can soak a ceiling in hours, and water near wiring or the disconnect is a real problem. Shut the system off at the thermostat first.

Why is my AC leaking water inside but not outside?

Indoor leaks point to the condensate side: a clogged drain line, a rusted pan, a dead condensate pump, or a coil that froze and is now thawing faster than the pan can drain.

Can I clear the condensate drain myself?

Many homeowners do, by attaching a wet/dry vac to the outdoor drain exit for a couple of minutes. If the clog does not clear or the pan refills, stop — repeated overflows usually mean a pan or pump problem.

How much does it cost to fix an AC leak?

A drain clear is typically the cheapest HVAC service call on the menu. A drain pan replacement, condensate pump, or refrigerant leak repair costs meaningfully more, and a frozen coil caused by low refrigerant means there is a leak to find first.

Keep reading

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