Why Is My Window Air Conditioner Leaking Water? Fixes

Your window air conditioner is leaking water because condensation that should drain to the outside is instead dripping inside or overflowing. The most common causes are a unit that isn’t tilted slightly toward the outside, a clogged drain channel or drain hole, a full or blocked drain pan, frozen evaporator coils that drip as they thaw, or loose seals that let humid outside air condense on the cold coils. Indoors-leaking units almost always trace back to tilt or a clogged drain. Start by confirming the unit is pitched slightly downward toward the exterior and that the drain path is clear, and you’ll fix the majority of window AC leaks.

Here’s how to tell which cause is yours, the order to check things in, and how to stop the leak safely.

Why is my window air conditioner leaking water?

It helps to know whether the water is leaking inside your home or outside. A small amount of water dripping outside is normal, that’s the condensation the unit is supposed to shed. Water leaking inside the room is the problem, and these are the usual causes:

• Wrong tilt: The unit must sit dead level side-to-side and pitch slightly down toward the outside. If it tilts inward, water runs into the room.
• Clogged drain hole or channel: Dirt, algae, or debris blocks the path, so water backs up and overflows inward.
• Full or blocked drain pan: Water has nowhere to go and spills over.
• Frozen coils: A dirty filter or low refrigerant can freeze the evaporator coils, which then drip as they melt.
• Loose seals: Gaps around the unit let warm, humid outdoor air reach the cold coils and condense.

How to fix a leaking window air conditioner

Work through these steps in order. Unplug the unit before removing any panels.

1. Check the tilt. With a level, confirm the unit is level side-to-side and pitched about a quarter inch lower at the back (outside). Adjust the mounting bracket or add a shim if needed.
2. Clear the drain. Find the drain hole/channel at the bottom rear and clear it of dirt, algae, and debris with a thin wire or a wet/dry vacuum.
3. Empty and clean the drain pan. Remove standing water and wipe out gunk that blocks drainage.
4. Check for ice. If you see frost on the coils, the unit is freezing up. Turn it off, let it thaw, then replace a dirty filter and clean the coils. If it keeps freezing, it may be low on refrigerant, which needs a technician.
5. Seal the gaps. Reseat the side panels and add weatherstripping or foam so humid outside air can’t seep in.

If the unit still leaks indoors after all of this, there may be an internal defect or a refrigerant problem, and it’s worth calling a professional.

How can I prevent my window air conditioner from leaking water?

• Install the unit with the correct outward tilt from the start.
• Clean or replace the filter every few weeks so coils don’t freeze.
• Flush the drain channel each season; a vinegar-water solution helps stop algae.
• Keep the side seals and weatherstripping intact to block humid outside air.
• In very humid rooms, run a dehumidifier and don’t set the AC colder than needed.

What could be causing my window AC to freeze and then leak?

A leak that comes and goes, with frost on the coils between drips, points to a freezing problem rather than a drainage one. The two most common reasons coils freeze are restricted airflow (a dirty filter or blocked coils) and low refrigerant from a leak. Restricted airflow is a safe DIY fix: turn the unit off, let the ice melt completely, then clean or replace the filter and clean the coils. Low refrigerant is not a DIY job, because handling refrigerant requires a licensed technician. If the coils refreeze soon after cleaning, have a pro check the charge.

My window air conditioner is leaking water, what should I do?

First, stop the immediate damage: turn the unit off, place a towel or pan under the leak, and unplug it before inspecting. Then run the checks above, tilt, drain, pan, ice, seals, in that order, since the first two solve most indoor leaks. If you’ve corrected the tilt, cleared the drain, and the unit still leaks inside, or if you find ice that keeps returning, call a technician. Persistent indoor leaks can damage walls, floors, and sills, so don’t let it run unaddressed.

How to fix a leaking window A/C indoors

Frequently Asked Questions

Why is my window air conditioner leaking water inside?

Almost always because the unit isn’t tilted slightly toward the outside or the drain is clogged, so condensation backs up into the room. Level the unit with a slight outward pitch and clear the drain channel first.

Is it normal for a window AC to drip water outside?

Yes. Dripping outside is the unit shedding the condensation it pulls from the air, which is normal, especially on humid days. Only water leaking inside the room is a problem.

Should I turn off a leaking air conditioner?

If it’s leaking indoors, yes, turn it off to prevent water damage while you find the cause. If you see ice on the coils, turning it off and letting it thaw is also the first step before cleaning the filter and coils.

Next Steps

A puddle around your window air conditioner is common and usually fixable. Confirm the unit is level with a slight outward tilt, clear the drain channel and pan, check for frozen coils, and reseal any gaps. Those steps resolve most indoor leaks. If the leak continues after you’ve corrected the tilt and drainage, or the coils keep freezing, bring in a technician to check the seals, refrigerant, and internal components before water damages your home.