Why Is My Air Conditioner Leaking Water?

Quick answer

An air conditioner leaking water usually has a clogged condensate drain, a full or overflowing drain pan, a window unit tilted the wrong way, or coils that froze and are now melting. Some water outside a window unit is normal; water inside is not. This guide is for beginners with a window, portable or central system who want safe checks before calling a qualified technician.

Safety first

• If water has reached an outlet, power cord or the unit’s electrical parts, don’t touch the unit, the plug or nearby switches. Switch off the breaker only if you can do it from a dry spot, and call a professional.
• Otherwise, turn the AC off and unplug it (or switch off its breaker, or turn central air off at the thermostat) before checking filters, drains or pans.
• Never remove panels or covers to reach internal parts, and never touch wiring or the sealed cooling system.
• Mop up standing water quickly to prevent slips and water damage, and dry damp areas within a day or two to limit mold growth, as the US EPA advises.

Before you begin

Some background helps. As an air conditioner cools, it pulls moisture out of the air. That water, called condensate, collects in a pan and leaves through a drain line or, for many window units, drips outside. Portable units collect it in an internal tank or evaporate it, depending on the design.

Look up your model’s manual to see how your unit handles condensate and how a window unit should be installed. Error codes, such as a “tank full” signal on a portable unit, vary by brand and model, so check the manual or the manufacturer’s support site.

Possible causes

Things you can check yourself:

• Window unit tilted toward the room. Most window units are meant to tilt slightly toward the outside so water drains away; your manual gives the exact guidance.
• Clogged condensate drain line. Algae, dust and debris can block the line, so water backs up.
• Full drain pan or portable unit tank. A full tank or pan can overflow.
• Dirty air filter and frozen coils. Poor airflow lets ice form; when it melts, more water drips than the pan can handle.
• Portable unit drain plug or hose. A loose plug or a hose that’s kinked or raised can let water escape.

Problems that need a technician:

• A cracked or rusted drain pan inside the unit
• A failed condensate pump (a small pump some central systems use to move water)
• Water leaking from inside the cabinet or ceiling
• Ice that keeps coming back, which can point to a sealed-system problem only a professional should handle

Safe checks for a leaking AC

1. Turn it off and protect the area. Switch the unit off, unplug it if the plug is dry and easy to reach, and lay towels down. Put a shallow pan under drips.
2. Check a window unit’s tilt. Place a small level on top of the unit, front to back. Compare with your owner’s manual, which says how the unit should tilt. Is it tilted toward the room? If yes, adjust the support brackets or shims as the manual describes, or ask someone to help you reinstall it safely. Never lean out of a window to do this. If it’s already correct, go to step 3.
3. Check the filter and look for ice. Slide out the filter and check for dust. Look at the coil area you can see with the filter out. Is there ice? If yes, turn cooling off and let it thaw completely, with towels in place, then put in a clean filter. See how to clean or replace an air conditioner filter.
4. Empty a portable unit’s tank. If your portable unit has a tank or drain plug, drain it as the manual explains, over a pan. Make sure any drain hose runs downhill without kinks and that the plug is fully closed afterward. Did the leak stop? If yes, empty or drain it as often as the manual suggests during humid weather.
5. Check the visible drain pan and line (central air). With the system off, look at the indoor unit with a flashlight for a drain pan you can see without removing panels, and the drain line leaving it (often a white plastic pipe). If the pan is full, soak up or vacuum the water with a wet/dry vacuum. Is the line clogged where it ends outside or at a floor drain? If yes, some owners’ manuals describe clearing the end with a wet/dry vacuum; follow your manual and don’t open the unit.
6. Restart and watch. After about an hour of normal cooling, check for drips. Is it dry? If yes, add filter and drain checks to your routine. If not, it’s time for professional help.

If the unit also isn’t cooling well, see air conditioner not cooling.

When to stop and call a qualified technician

Call a qualified HVAC or appliance technician, or the manufacturer’s service network, if:

• Water is near outlets, wiring or the unit’s electrical parts
• Water is dripping from a ceiling, wall or the inside of the cabinet
• The drain pan is cracked, rusted or hidden behind panels
• The condensate pump isn’t working or makes unusual noises
• Ice keeps returning after you’ve cleaned the filter and let it thaw
• The leak continues after you’ve checked tilt, filter, tank and visible drain

For water damage to floors or walls, act quickly to dry the area and consider the EPA’s guide to mold and moisture.

FAQ

Is it normal for a window AC to drip outside?

Yes. Many window units send condensate out the back, so dripping outdoors on a humid day is usually normal. Water dripping inside the room is the sign of a problem.

Why is my AC leaking water inside the house?

Common reasons are a clogged drain line, an overflowing pan, a dirty filter that caused the coils to freeze and then melt, or a window unit tilted toward the room. Start with those checks.

Can a dirty filter make an air conditioner leak?

Yes. A clogged filter reduces airflow, ice can form on the coil, and the meltwater may overflow the pan. Cleaning or replacing the filter is an easy first step.

Should I keep running my AC while it’s leaking?

It’s best to turn it off until you find the cause, especially if water is near electrical parts. Running it can spread water damage and, with frozen coils, make the ice worse.

Do refrigerators leak for similar reasons?

Sometimes, since both make condensate. See why is my refrigerator leaking water? for fridge-specific checks.