Why Is My AC Leaking Water? Find where it’s coming from and what to do right now

Your AC most often leaks water because the condensate drain line is clogged, and where the water shows up tells you how urgent it is.

A thin drip from the outdoor drain pipe is normal. Water inside your home, from a vent, or through a ceiling is not.

If water is inside, turn off the AC at the thermostat before you do anything else.

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Is it normal for an AC to leak water?

Yes, but only in one place: outside, at the end of the drain pipe, while the system is cooling. Water anywhere inside your home means the drain path is blocked, broken, or overwhelmed.

How an air conditioner makes water

Condensate is the water that forms when warm, humid indoor air touches the cold evaporator coil, and its moisture condenses.

It drips into a pan under the coil and runs out through a drain line, usually a PVC pipe that ends outside or at a floor drain. Cooling removes humidity along with heat, so some condensate is normal.

Normal vs. not normal: what counts as a leak

Situation	Normal?	What it means
Light drip from the outdoor drain pipe while cooling	Yes	Condensate is leaving by its intended path.
Meltwater under a heat pump’s outdoor unit in winter	Yes	The unit is shedding frost during its defrost cycle.
Puddle, drip, or damp spot indoors	No	The drain path is blocked, cracked, or overflowing.
Humid house or musty smell, but no outdoor drip after an hour of cooling	Investigate	Water may be backing up in the line or pan.
Ice on the coil or refrigerant lines	No	Airflow or refrigerant is off, and the melting ice will overflow the pan.

Why is my AC dripping water after turning off?

A brief drip for a few minutes after shutdown is normal, because the coil and pan are still draining leftover condensate.

• Normal: dripping that tapers off within a few minutes and leaves no pooled water indoors.
• Not normal: dripping that continues for an hour or more, or water that pools, which points to a blocked drain line or a cracked pan holding water that then escapes.

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Where is the water coming from? Triage by location

Water near the indoor unit, at a vent, or on a ceiling points to a blocked or overflowing drain path, while water at the outdoor pipe is usually normal.

Find your spot in the table to see the likely cause and how soon to act.

Where you see water	AC type	Most likely cause	Urgency	Details
Puddle around the indoor unit or air handler	Central	Clogged drain line or cracked pan	Within 24 hours	Clogged line
Water on the wall or floor under the indoor unit	Split	Kinked or blocked drain hose, unit not level	Within 24 hours	Indoor unit fix
Water dripping from vents	Central	Overflowing pan or melting ice	Act now	Frozen coil
Ceiling stain or drip	Central	Overflowing pan or backed-up line	Act now	Vents and ceilings
Water on the sill or inside the room	Window	Wrong tilt, clogged drain, dirty filter	Within 24 hours	Window AC
Dripping from the outdoor pipe	All	Normal condensate	Monitor	Outdoor pipe

Why is my AC leaking water from the bottom?

• Water under a central air handler usually means the primary pan overflowed because the drain line is clogged.
• Water under a wall-mounted split unit usually means the drain hose is blocked, kinked, or sloping the wrong way.
• Water pooling around a basement or closet unit can come from a failed condensate pump.

Water from vents or through the ceiling

• Water dripping from a vent means the pan overflowed into the ductwork or a frozen coil is thawing into it.
• A ceiling stain below an attic or closet air handler means the drywall is already wet, so treat it as urgent.
• A bulging or sagging ceiling can collapse, so keep people and pets out from under it.

Water dripping from the outdoor pipe or unit

The drain pipe outside a central system, or the hose outlet on a split system, is supposed to drip while the AC cools. The amount rises with humidity.

• Normal: a steady drip or a small wet patch below the pipe on a humid day means the drain is working.
• Not normal: a gush of water, a flow that continues long after shutdown, or ice around the pipe means something upstream has failed.

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What to do first when your AC is leaking water

Turn the AC off, stop the water from spreading, and then look for the source.

The first 10 minutes: stop the damage

1. Switch the AC off at the thermostat or switch to completely cut off electrical power.
2. If water is near outlets or the electrical panel, turn off the breaker only if you can reach it without standing in water.
3. Catch the drip with a bucket and soak up standing water with towels.
4. Move furniture, rugs, and electronics out of the wet area.
5. Check the air filter and look for ice on the coil or refrigerant lines.
6. Photograph the water and any damage with the date visible.

Should I turn my AC off if it’s leaking?

Yes, whenever water is getting into your home. A running system keeps producing condensate that a blocked line cannot carry away, and an iced coil keeps freezing.

Fan-only mode is the one exception, because moving air thaws a frozen coil. A light drip at the outdoor pipe needs no shutdown.

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Why is my AC leaking water? The most common causes

1. A clogged condensate drain line
2. A dirty air filter
3. A frozen evaporator coil
4. A cracked or overflowing drain pan
5. A failed condensate pump or float switch
6. A unit that is not level or was poorly installed

What is the main reason for water leakage in an AC?

A clogged condensate drain line is the main reason. Dust, algae, and mold build up as slime inside the line until water backs up, fills the pan or water tray, and spills over.

Clogged condensate drain line

• Water pools around the indoor unit while the outdoor pipe stays dry.
• The pan holds standing water or feels slimy.
• A musty smell comes from the unit or the vents.
• The system shuts off if a float switch is installed.

The full steps are in our guide on how to clean an AC condensate drain line.

Dirty air filter

A filter packed with dust restricts the air moving across the coil. With less warm air reaching it, the coil gets cold enough to freeze.

• The ice melts faster than the pan and line can handle.
• Replacing the filter fixes many of these leaks, and it is the cheapest thing to check first.

Frozen evaporator coil

Restricted airflow and low refrigerant are the usual reasons a coil freezes. Running the AC when it’s cool outside can do it too.

• You can see ice behind the access panel or frost on the copper line.
• Airflow from the vents feels weak.
• Water appears only after the system shuts off and the ice melts.

If your coil is already iced over, here is how to thaw a frozen AC evaporator coil without damaging it.

Cracked or overflowing drain pan

Metal pans rust through and plastic ones crack with age, so a pan can leak even when the drain line is clear. A technician should replace it, because sealing is a temporary patch at best.

Failed condensate pump or float switch

A condensate pump pushes water uphill or out of the house when the unit sits below the drain, as in a basement or closet. When it fails, its reservoir overflows.

A float switch is the safety that cuts power when the pan fills.

• Water pools around the pump reservoir.
• The AC stops cooling with water sitting in the pan.

AC not level or poorly installed

A unit that is out of level, or a drain hose that sags or slopes the wrong way, sends water to the wrong place.

This is the most common reason a new AC leaks in its first days. A split system’s drain hose must slope downward along its whole length with no dips, and a window unit must tilt slightly toward the outside.

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Water leak or refrigerant leak? How to tell

Water from an AC is almost always condensate, not refrigerant. Refrigerant stays sealed in copper lines and escapes as a gas, so it rarely leaves a puddle.

A refrigerant leak can still cause a water leak indirectly: low refrigerant lets the coil freeze, and the ice melts into your pan.

Clue	Condensate (water)	Refrigerant leak
Appearance	Clear and thin, like water	Oily film at line fittings, little visible liquid
Where it shows	Pan, drain line, floor below the indoor unit	Line joints, coil, outdoor unit connections
Cooling	Normal until the line backs up	Weak cooling and longer run times
Sound	Quiet, sometimes gurgling	Hissing or bubbling near the lines
Urgency	Act within hours if water is indoors	Book a technician soon, and don’t keep running an iced system
Who fixes it	You, for a filter or a drain clog	A technician certified under EPA Section 608

Don’t rely on smell to tell them apart. Modern refrigerants are hard to detect by odor.

Signs the liquid is condensate, not refrigerant

• The liquid is clear and thin, with little or no odor.
• It collects near the pan, the drain line, or the floor below the indoor unit.
• Cooling still works normally.

When low refrigerant is the real cause

Learn the signs of an AC refrigerant leak if the symptoms in the table fit. Refrigerant is not consumed like fuel, so a low system has a leak somewhere.

Topping it off without finding the leak only delays the next freeze-up, and handling refrigerant takes EPA certification in the United States.

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How to fix water leaking from an AC indoor unit

To fix water leaking from a split AC indoor unit, turn it off, clean the filter, and clear the drain hose, then check that the unit and hose slope correctly.

1. Switch the unit off and turn off its breaker.
2. Pull out the filter, rinse it, and let it dry.
3. Check the drain hose at its outdoor end for kinks, loops, or a blocked outlet.
4. Clear a blockage by sucking from the outlet with a wet/dry vacuum, or by flushing the hose with water.
5. Sometimes, you will need to open up the AC, remove the water tray, and wash away the mucus on the water tray, then fix it back ( this action should be done by an HVAC technician).
6. Confirm the hose slopes downward along its whole length.
7. If the front panel shows ice, run fan-only mode until it melts, then restart in cool mode.
8. Run the unit for 30 minutes and watch the indoor unit. If water still drips, call a technician, because the cause may be refrigerant or the unit’s tilt.

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Why is my window AC leaking water?

A window AC leaks when it isn’t tilted slightly toward the outside, when its drain pan or drain hole is clogged, or when a dirty filter lets the coil ice up.

Gaps around the frame can also let rain in. Follow these steps.

1. Turn the unit off and unplug it.
2. Check the tilt: the back should sit a little lower than the front so condensate runs out the rear. Shim the unit if it doesn’t.
3. Clean the filter.
4. Brush out the base pan and the drain hole at the back.
5. Look for ice on the coil, and run fan-only mode to melt it.
6. Seal gaps around the frame with foam or weatherstripping, then run the unit and check it after 30 minutes.

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Why is my air conditioner leaking water in my apartment?

The causes are the same as in a house, with a clogged drain line first, but apartments add two wrinkles: a ceiling leak may come from the unit above yours, and you may not control the system.

• Switch your unit off and keep it off until the source is found.
• Photograph the damage with dates before you clean up.
• Tell maintenance in writing right away, and ask whether a neighbor’s unit or a shared drain could be involved.

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How to fix a leaking AC: DIY or call a pro

You can fix most leaks yourself when the cause is a dirty filter, a clogged drain line, or an out-of-level window unit.

Call a technician for ice that keeps returning, a cracked pan, a failing pump, a suspected refrigerant leak, or any water near electrical equipment.

Can I fix an AC Water leak myself?

Yes, for the filter and drain line. Work in this order.

1. Turn the AC off at the thermostat, and at the breaker if water is near electrical equipment.
2. Replace or rinse the air filter.
3. Find the drain line outlet outside and the access port on the indoor unit.
4. Hold a wet/dry vacuum to the outlet for a minute or two to pull out the clog.
5. Pour a cup of white vinegar into the access port, wait 30 minutes, then flush with water.
6. Dry the pan if you can reach it.
7. Restart the system and watch it for 30 minutes.

When to call an HVAC technician

• Ice returns within a day or two of thawing the coil.
• Water keeps appearing after you have cleared the drain and changed the filter.
• The condensate pump hums but doesn’t move water, or never shuts off.
• Water has reached outlets, the electrical panel, or a ceiling that sags.

What AC leak repairs typically cost

These are typical US ranges, and they vary by region; consult HVAC technicians in your locality for prices.

Repair	Typical US range	Notes
DIY drain flush	$0 to $50	White vinegar, a wet/dry vacuum, and a new filter
Professional drain line clearing	$150 to $300	Often includes a flush and inspection
Float switch part	$25 to $50	Labor is extra
Condensate pump replacement	$250 to $450	Higher when the unit is hard to reach

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Is water dripping from an AC dangerous?

Water from an AC is rarely dangerous by itself, because it is mostly clean condensate, but where it lands can be: near electrical equipment, above a ceiling, or soaking building materials for days.

Mold and water-damage timeline

In humid climates, a whole-home dehumidifier can remove approximately 15 U.S. gallons (57 litres) of water from indoor air per day, although the actual amount depends on the unit’s capacity, indoor humidity, temperature, and operating time. For example, Trane states that one of its whole-house dehumidifiers can remove up to 120 pints—15 gallons—of water per day.

With a blocked drain line, much of that ends up in your ceiling or floor.

Time since the leak starts	What is happening	What to do
0 to 1 hour	Water spreads across the floor and starts soaking drywall, carpet, and insulation.	Switch off the AC, stop the source, and remove standing water.
Same day	Porous materials wick moisture upward and sideways.	Run fans and a dehumidifier, move furniture, and lift wet rugs.
24 to 48 hours	The EPA’s recommended window for drying water-damaged materials closes, and mold can start on damp surfaces.	Pull wet carpet padding and soaked insulation, and keep drying.
48 to 72 hours	Restoration firms commonly report visible mold in this window.	Call a restoration company if materials are still wet.
1 week or more	Established mold is likely, and wet drywall may need replacing.	Have the area inspected and expect to cut out damaged material.

Many building codes require overflow protection where a leak could damage the structure.

Under IMC Section 307.2.3, HVAC equipment that produces condensate generally requires auxiliary or secondary overflow protection, such as a separate drain, an auxiliary drain pan, or a listed water-level detection device that shuts off the equipment if the primary drain is blocked. Because local jurisdictions may amend the IMC, verify the requirements adopted in your area.

Electrical and ceiling hazards

• Water near outlets, wiring, or the electrical panel can cause shock, so stay out of standing water and cut power only from a dry spot.
• A ceiling holding water can collapse without warning, so keep people away from sagging areas.
• Lingering dampness can grow mold, which can irritate the airways of people with asthma or allergies.

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How to stop your AC from leaking again

Change the filter on schedule, flush the drain line every year, and add an overflow switch so a future clog shuts the system off instead of flooding your ceiling.

Maintenance schedule

Task	Frequency	DIY or pro
Check or replace the air filter	Monthly during heavy use	DIY
Flush the drain line with white vinegar and water	At least once a year, more often in humid climates	DIY
Test the float switch	Once a year	DIY or pro
Inspect the pan, coil, and pump	Before cooling season	Pro

Our seasonal AC maintenance checklist covers the full pre-season inspection.

Safety devices worth installing

• A float switch cuts power to the system when the pan fills, so a clog stops the AC before water spills.
• A secondary drain pan under an attic or closet air handler catches overflow before it reaches the ceiling.
• A battery-powered water sensor near the unit sounds an alarm at the first sign of moisture.

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If water keeps returning after you have cleared the drain and changed the filter, the cause is probably deeper than a clog: a cracked pan, a failing pump, or a refrigerant leak that keeps freezing the coil.

Booking an AC leak repair service gets you a drain-line and leak inspection, a repair that fixes the source, and an overflow switch so the next blockage stops the system instead of flooding your home.

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Frequently asked questions