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Window AC Leaking Water Inside? The Tilt Check and a Drain Hose

Window ACs make water as they cool, and it should drain outside. Check the tilt, clear the drain, and add a hose if yours has a drain port.

By Jamilur Rahman Updated November 5, 2026 · 6 min read

Time
30 min
Cost
Under $20
Difficulty
Easy
A window air conditioner in a window with a small puddle of water and a towel on the sill under it
In this guide
  1. Quick answer
  2. Free vs. permanent fix
  3. What you'll need
  4. Why it happens
  5. Try this first (free)
  6. When free fixes aren't enough
  7. Buy the fix
  8. Leaking in the rain, not from the AC
  9. What to skip
  10. FAQ
  11. Related problems

Quick answer

Why is my window AC unit leaking water inside? Usually the unit is tilted slightly toward the room, or its drain holes or filter are clogged, so the water it pulls from the air runs inward instead of outside. Tilt it a little toward the outdoors, clean the filter and drain holes, and if your unit has a drain port, a drain hose carries the water away.

Free fix vs. permanent fix

Free fix · 20 minutes

Check the tilt, filter and drain holes

  • Unplug the unit and set a level on top
  • Shim the back of the unit lower than the front
  • Wash the filter and clear the drain holes in the base
  • Check that the unit is not frozen or full of water

How long it lasts: Often permanent if the tilt was the cause. Dirt and humid weather can bring the leak back.

Most readers choose Permanent fix
Window AC drain hose kit (illustration)
Illustration

A window AC drain hose kit

In humid weather the unit pulls out more water than the pan can drain. A hose on the drain port sends it to a bucket or outdoors, so it cannot spill back. Not every model has a drain port, so check the manual.

What to get: Window AC drain hose kit

How long it lasts: Years. It carries water away so the pan cannot overflow into the room.

Check price on Amazon

As an Amazon Associate I earn from qualifying purchases.

What you'll need

  • Bubble level

    Or a level app on your phone

    You have it

  • Towels and a shallow pan

    To catch water while you work

    You have it

  • Pipe cleaner or soft wire

    To clear the drain holes

    Free
  • Wooden shims (illustration)
    Illustration

    Wooden shims

    To tilt the unit slightly back toward the outside

    Check price
  • Our pick
    Window AC drain hose kit (illustration)
    Illustration

    Window AC drain hose kit

    Only if your unit has a drain port or plug

    Check price
  • Window AC support bracket (illustration)
    Illustration

    Window AC support bracket

    Holds the unit level and stops it from sagging

    Check price

Why it happens

1

The unit tilts toward the room

Cooling makes water, and the unit is meant to drain it out the back. If it sits level or tips inward, the water spills into the room.

2

Clogged drain holes or pan

Dirt and algae block the small holes in the base. The pan fills up and overflows, usually from the front or the bottom edge.

3

A dirty filter or coil

Blocked airflow makes the coil too cold. Ice builds up and then melts faster than the pan can drain.

4

Humid weather

On a very humid day the unit pulls in much more water than usual, and some of it runs the wrong way.

5

Gaps around the window

Rain can run through gaps around the unit. If it only leaks when it rains and the AC is off, it is not condensation.

Try this first (free)

Do these in order, starting with the simplest.

  1. Unplug it and check the tilt

    Tool used: Bubble level

    Set a level on the top of the unit. It should tilt slightly toward the outside, roughly a quarter to a half inch lower at the back. Check the manual, since some newer models are built with the slope inside and want to sit level.

  2. Fix the tilt with shims

    Tool used: Wooden shims

    Slide wooden shims under the back edge or the support rails until the back is slightly lower. Do not tilt it far, since the unit can slip out of the window.

    Wooden shims (illustration)
    Illustration

    Tool for this step

    Wooden shims · To tilt the unit slightly back toward the outside

    Check price on Amazon

  3. Wash the filter

    Pull the front grille and slide out the filter. Rinse it with warm water and mild soap, then let it dry before you put it back.

  4. Clear the drain holes

    Tool used: Pipe cleaner or soft wire

    Look along the bottom of the unit and the back for small holes or a drain plug. Poke a pipe cleaner through them to clear dirt. Pour the pooled water into a pan and wipe the base dry.

  5. Add a drain hose if your unit has a port

    Tool used: Window AC drain hose kit

    Look in the manual for a drain port or plug. If there is one, attach a hose, point it downhill to a bucket or outdoors, and keep it free of kinks.

    Window AC drain hose kit (illustration)
    Illustration

    Tool for this step

    Window AC drain hose kit · Only if your unit has a drain port or plug

    Check price on Amazon

When free fixes aren't enough

If the unit is level and clean and still drips on humid days, it makes more water than the base can drain by gravity. A drain hose gives that water a way out. If the unit has no drain port, a support bracket and a better tilt are the fix. If the coil is iced over, water is leaking from the front only after the ice melts, so see the page on window ACs freezing up. A unit that drips water onto an outlet, cord or electrical parts should be unplugged and checked before you run it again.

Buy the fix

Still stuck after the free fixes? These are the products we would look at.

Our picks compared
PickProductFixesWho it's forBuy
Best pick
Window AC drain hose kit (illustration)
Illustration
Window AC drain hose kit
water that overflows the pan and drips inside Anyone with a window unit that has a drain port and leaks on humid days. Check price
Upgrade pick
Window AC support bracket (illustration)
Illustration
Window AC support bracket
a unit that sags or tilts into the room Anyone whose window sill is soft, sloped or too narrow to hold the unit level. Check price
Best pick
Window AC drain hose kit (illustration)
Illustration

Window AC drain hose kit

Fixes: water that overflows the pan and drips inside

Look for: A fitting that matches your unit's drain port, so check the model; A hose long enough to reach a bucket or the outdoors; A hose that bends without kinking.

Who it's for
Anyone with a window unit that has a drain port and leaks on humid days.
Honest downside
Your unit has no drain port or the manual says to leave the plug in. Use the tilt and the clean-out steps instead.
Check price on Amazon
Upgrade pick
Window AC support bracket (illustration)
Illustration

Window AC support bracket

Fixes: a unit that sags or tilts into the room

Look for: A weight rating above your unit's weight; Adjustable arms for your wall or sill; Stable mounting hardware that suits your window.

Who it's for
Anyone whose window sill is soft, sloped or too narrow to hold the unit level.
Honest downside
You rent and cannot drill. Check your lease before you mount a bracket.
Check price on Amazon

As an Amazon Associate I earn from qualifying purchases. We don't show prices because they change, so use the button to see today's price.

How we picked: How we picked: this page is based on room air conditioner troubleshooting guides from manufacturers, installation manuals, and the problems and fixes people report in reviews of drain hoses and brackets. We do not test products by hand.

Leaking in the rain, not from the AC

If water only comes in when it rains, even with the AC off, it is a seal problem, not condensation. Check the foam strip and the accordion side panels for gaps, and seal them with weather stripping or foam.

What to skip

Towels and a bucket as a permanent fix

A towel on the sill only hides a leak that is soaking the wall or floor. Water in the wrong place can damage the window frame and walls. Fix the tilt or drain, then use a towel only while you wait.

Frequently asked questions

Why does my window AC unit keep leaking water inside?
If the cause is the tilt or a blocked drain, it will keep leaking until you fix it. Check the tilt first, then clear the drain holes and wash the filter. If it only drips on humid days, a drain hose may be the answer.
Why is my window AC leaking from the front?
The unit is probably level or tipped toward the room, so the pan overflows toward the front. A frozen coil melting also drips from the front. Tilt it back slightly and clean the filter.
Why is my window AC spitting water, or full of water?
Many units use a fan ring to throw pooled water onto the coil, which can make a spitting or splashing sound outdoors. It is normal in moderation. If water collects in the base and spills inside, the drain holes are blocked or the tilt is wrong.
Should a window AC tilt?
Most should tilt slightly toward the outside. Manufacturer guidance usually says about a quarter to a half inch, but check your manual because some models need little or none.
Is it safe to run an AC that is leaking?
A small drip onto the sill is fine. Water near a plug, a cord or the control panel is not, so unplug it and let it dry out first.

As an Amazon Associate I earn from qualifying purchases. Affiliate disclosure

Window AC drain hose kit (illustration)
Illustration

Our pick: Window AC drain hose kit

Check price