Alpha & Omega HVAC Appliance Repair · Orange County, CA · Updated 2026-08-11

AC Leaking Water? Why Your Air Conditioner Drips Inside: and What to Do

Key takeaways

The first move is always the same: switch the thermostat from COOL to OFF (leaving the fan on is fine) and put a pan under the drip, the system makes more water every minute it runs.
A clogged condensate drain is the overwhelming favorite cause; Orange County attics grow algae in the line by late summer.
The DIY that works is sealing a wet/dry vacuum to the outdoor drain stub and pulling the clog out, not forcing air or water in from the outside.
Other causes, in order: a rusted or cracked drain pan, a frozen coil melting faster than the drain can carry, a loose or sagging drain line, and a failed condensate pump.
A leak that comes with ice or weak cooling is an airflow or refrigerant problem, not just a drain problem.

Water dripping from around your indoor AC unit, a stain spreading on the ceiling below the attic air handler, or a puddle by the furnace closet, an air conditioner "leaking water" alarms people, and fair enough: the water can do more damage than the underlying failure costs to fix. The good news is that the causes are few, and the first move is always the same. In most of the homes we service across Irvine, Tustin and Lake Forest the air handler sits in the attic or a hallway closet, which is why this leak usually announces itself as a ceiling stain rather than a puddle.

First: Turn the Cooling Off

Every minute the AC runs, it pulls more moisture out of the air and makes more water. Switch the thermostat from COOL to OFF (leaving FAN on is fine), put a towel or pan under the drip, and the situation stops getting worse. Now it's a repair, not an emergency.

Cause #1: A Clogged Condensate Drain

The overwhelming favorite. Your AC's evaporator coil condenses gallons of water on a humid day, and it all leaves through a modest PVC drain line. In Orange County's warm attics that line grows algae, and by late summer it clogs. Water backs up into the drain pan, overfills it, and finds its way into your ceiling or floor. If your system has a float switch, it cuts the AC off first, which is why a clogged drain sometimes looks like a dead AC rather than a leak.

DIY that works: find the drain stub outside (a small PVC pipe near the outdoor unit or foundation), seal a wet/dry vacuum to it, and run it for a minute or two. If a slug of algae comes out and water follows, you've likely fixed it. What we don't recommend: forcing pressurized air or water from the outside inward, that can drive the clog deeper or pop a glued fitting hidden in a wall.

Cause #2: A Rusted or Cracked Drain Pan

Under the evaporator coil sits a drain pan; many systems have a secondary pan under the whole air handler in the attic. Metal pans rust through after 15–20 years, plastic ones crack. The symptom is a leak that continues even though the drain line is clear. Pans are replaceable, this is a normal repair, not a death sentence for the system.

Cause #3: A Frozen Coil, Melting

If the evaporator coil ices over, from a clogged filter, weak blower, or low refrigerant, the ice eventually melts faster than the drain can carry it away, and overflows the pan. The telltale: the leak appears right after the system shuts off, or you've noticed weak, warm airflow beforehand. Ice is its own problem with its own causes, see why an AC freezes up.

Cause #4: A Disconnected or Badly Sloped Drain Line

Sometimes the fitting at the pan simply comes loose, or the line was run with a sag where sludge settles and blocks flow. Common after attic work, pest-control visits, or any job where someone was crawling near the air handler.

Cause #5: A Failed Condensate Pump

Systems in garages, basements, and some closets can't drain by gravity, so a small pump pushes the water out. When the pump or its float sticks, the reservoir overflows quietly. If you can find the little box with tubes near your air handler, check whether it's full to the brim.

When to Call

Call us at (310) 600-8152 if the vacuum trick doesn't clear it, if the leak returns within days, if you see rust or standing water in the pan, or if the leak comes with ice or weak cooling, that points at airflow or refrigerant, which is AC repair territory. A cleared drain, flushed line, and tested float switch are also part of every AC maintenance visit, the cheapest way to never meet this problem in August.

Frequently Asked Questions

Why is my AC leaking water inside the house?

Almost always a condensate problem: the AC removes moisture from the air, and that water normally leaves through a drain line. A drain clogged with algae, a rusted or cracked drain pan, a disconnected drain line, or a frozen evaporator coil melting off after the system shuts down are the usual causes.

Is water leaking from the AC an emergency?

Turn the cooling off promptly, continued running keeps producing water, and ceiling or drywall damage costs far more than the AC repair. With the system off, the leak stops being urgent; it can usually be fixed in a single visit.

Can I unclog the AC condensate drain myself?

Often, yes. Find the PVC drain stub outside near the outdoor unit or foundation and pull the clog out with a wet/dry vacuum sealed to the pipe for a minute or two. What we don't recommend is forcing pressurized water or air toward the indoor unit, that can blow the clog deeper or pop a fitting inside a wall.

What is the float switch and why did my AC shut off?

A small safety switch in or near the drain pan that cuts the AC off before an overfilled pan overflows into your ceiling. If your AC quit on a humid week and there's water around the indoor unit, a tripped float switch from a clogged drain is a prime suspect, it's protecting your home.