Why Is My AC Leaking Water? 6 Causes & When to Call a Pro

A little condensation is normal - a puddle is not

Your air conditioner naturally pulls humidity out of the air, and that moisture has to go somewhere. Normally it drips into a pan and drains away quietly through a pipe. So a few drops at the outdoor drain line is fine. Water pooling around your indoor unit, dripping from a vent, or staining a ceiling is not - and because water damage compounds fast, it's worth acting on the same day.

Here are the six most common reasons an AC leaks water, and which you can handle yourself.

Quick takeaways:

• The #1 cause is a clogged condensate drain line - often a DIY fix
• A frozen coil that melts dumps far more water than the pan can hold
• Turn the AC off first to stop the leak and prevent water damage
• If you smell something chemical or hear hissing, it may be refrigerant, not water - that's a safety issue, call a pro
• Ceiling stains or attic-unit leaks need prompt attention to avoid drywall damage

First: shut the system off

Before troubleshooting, turn the AC off at the thermostat. Running it while it leaks just adds more water and risks damaging the unit and your floors or ceiling. Mop up standing water so you can see where it's actually coming from.

1. Clogged condensate drain line (most common)

The drain line carries condensation outside. Over time it clogs with algae, dust, and slime, so water backs up and overflows the pan. Many systems have a float switch that shuts the AC off when the pan fills - which is actually a clue pointing here.

DIY fix: find the drain line (a PVC pipe near the indoor unit, usually ending outside), and use a wet/dry vacuum at the outdoor end to suck out the clog. Pouring a cup of distilled vinegar into the drain access port a few times a year keeps it clear.

2. Frozen evaporator coil that melted

If the indoor coil freezes into ice and then thaws, it releases far more water at once than the drain pan can handle, so it overflows. The leak is really a symptom of the freeze. Common triggers are a dirty filter or low refrigerant - our guide on why an AC freezes up covers the fixes, and replacing a dirty air filter is the first thing to rule out.

3. Cracked or rusted drain pan

The pan under the coil catches condensation. On older systems (15+ years), it can rust through or crack, so water drips straight past it. A pan replacement is inexpensive but usually a pro job because of access.

4. Broken condensate pump

If your indoor unit is in a basement or anywhere below the drain exit, a small condensate pump pushes the water up and out. When that pump fails, water has nowhere to go and overflows. You'll often notice the pump isn't humming. Pumps are a straightforward pro replacement.

5. Dirty air filter

It comes up again because it causes so many problems: a clogged filter reduces airflow, freezes the coil, and leads to overflow when the ice melts. It's the cheapest thing to rule out first.

6. Refrigerant leak (this is different - and a safety issue)

If the "leak" isn't water but feels oily, smells chemical, or comes with a hissing sound and warm air, you may have a refrigerant leak rather than a condensation problem. Refrigerant is not something to handle yourself - ventilate the area and call a licensed technician.

What you can safely DIY vs. what needs a pro

Safe to try yourself:

• Turning the system off and drying up the water
• Clearing the condensate drain line with a wet/dry vac
• Replacing a dirty filter
• Pouring vinegar down the drain access to prevent re-clogging

Call a licensed pro for:

• A cracked or rusted drain pan
• A failed condensate pump
• A coil that keeps freezing
• Any suspected refrigerant leak (chemical smell, hissing)
• Ceiling or attic leaks where water is reaching drywall

Bottom line

Most AC water leaks come down to a clogged drain line or a coil that froze and melted - both of which you can often handle in under an hour. Turn the system off first to stop the damage, clear the drain, and check the filter. If the pan, pump, or refrigerant is involved, that's a quick pro repair.

If the leak won't stop or it's reaching a ceiling, don't risk the water damage - connect with a licensed local AC pro for same-day service, with upfront pricing.