If your AC is leaking water inside, turn it off and wipe up the water. The most common cause is a clogged condensate drain line that makes the drain pan overflow. Other causes include a cracked pan, a tripped float switch, a failed condensate pump, or a frozen coil that's thawing. If you can't find and clear the cause, call a technician.
Fallbrook Heating & Air has fixed air conditioners across North County since 1972, and water leaks are a steady summer call. A leak is rarely dangerous to the AC itself, but it can quietly damage ceilings, floors and drywall. Acting quickly is what keeps a small repair from becoming a bigger one.
Water and electricity. If water is near outlets, cords, the air handler's wiring or a furnace, switch the system off at the breaker before you touch anything. Don't open the unit's panels. If a ceiling is sagging or bulging with water, stay out from under it, and if water is dripping through a light fixture, turn that circuit off at the panel. EPA advises drying water-damaged materials within 24 to 48 hours to help prevent mold.
Why is my AC leaking water?
Your AC's indoor coil removes moisture from the air as it cools. That water drips into a drain pan and flows out through a condensate drain line. When the line clogs, the pan cracks, or a pump fails, the water has nowhere to go and spills out around the unit or through a ceiling.
On a humid day, a working system can drain several gallons. Fallbrook summers are mostly dry, but muggy spells push more water through the drain, and that's often when a partly blocked line finally overflows.
| Cause | Sign | Can you fix it yourself? | Typical fix |
|---|---|---|---|
| Clogged condensate drain line | Full drain pan; no water at the outside drain outlet | Partly (follow the manufacturer's instructions) | Clear and flush the drain line |
| Full, cracked or rusted drain pan | Water under the unit even when the line flows; visible rust | No | Repair or replace the pan |
| Tripped float switch | AC suddenly stops cooling; pan or line full of water | Partly (it resets once the water drains) | Clear the drain; replace a faulty switch |
| Frozen coil thawing | Ice on the copper lines; leak starts after the AC shuts off | Partly | Thaw, replace the filter; technician if it refreezes |
| Failed condensate pump | Pump reservoir full; pump silent or running nonstop | Partly (check that it's plugged in) | Repair or replace the pump |
| Attic air handler overflow | Ceiling stain below the attic unit; water dripping from the overflow outlet | No | Clear the primary drain; check or replace the overflow pan and switch |
What should I do first?
Turn the AC off at the thermostat, and at the breaker if water is near anything electrical. Wipe up standing water, put towels or a shallow pan down, and move belongings out of the way. Then look at the drain pan, the float switch, and where the drain line exits outside. Note any ceiling stains.
Quick checks you can do safely
- System off. Set the thermostat to OFF. Running the AC keeps making water.
- Drain-line access. Many systems have a capped vertical port (often a T fitting) on the drain line near the indoor unit. If water is standing right at the top, the line is clogged downstream. To clear it, follow the manufacturer's instructions or call us.
- Outside drain outlet. Find where the line exits, often near the outdoor unit or through a wall. In summer it should drip while the AC runs. Make sure it isn't buried in mulch or blocked by plants.
- Float switch. Look for a small switch on the drain pan or drain line. If the pan is full, it has probably tripped. Once the water drains, it usually resets on its own.
- Condensate pump. If your unit pumps water uphill, check that the pump is plugged in and listen for it. A full reservoir with a silent pump points to a failed pump.
- Ice. Check the copper lines for ice. If you see it, follow our frozen AC guide.
- Ceilings and walls. Look for stains, bubbling paint or soft drywall, especially below an attic unit. Take photos for your records.
Don't pour bleach, drain cleaner or other chemicals into the drain line. Some products can damage pans, pumps and fittings. If the line needs cleaning, follow the manufacturer's instructions or call us.
Why is my attic AC leaking through the ceiling?
Many Southern California homes have the air handler or furnace in the attic. Under it sits a secondary overflow pan meant to catch water if the primary drain fails. If that pan is full, cracked, or its drain or float switch has failed, water comes through the ceiling. A ceiling stain is often the first warning.
Some overflow pans drain to an outlet over a window or under the eaves, placed where you'll notice it. If you ever see water dripping from that outlet, the main drain is blocked, even if nothing is leaking inside yet. Turn the AC off and call us. Don't climb into a hot attic or walk off the framing to look.
Can a frozen coil cause a leak?
Yes. When an AC freezes from low airflow or low refrigerant, the ice melts once the system shuts off, and more water reaches the pan than it can handle at once. If the leak follows ice on the lines, fix the freeze, not just the drain.
A coil that freezes repeatedly with a clean filter often points to low refrigerant. That means a leak, and handling refrigerant requires EPA Section 608 certification. See our refrigerant leak repair page.
Is the water from my furnace instead?
It might be. High-efficiency furnaces produce their own condensate in heating season and drain it through PVC piping, often sharing a drain or pump with the AC. If water appears in winter with the AC off, see our furnace not working guide.
When to call a technician
Call when water keeps returning after you've checked the drain outlet and the float switch, when the pan is cracked or rusted, when the condensate pump has failed, when a ceiling below an attic unit is stained, or when the leak follows ice on the lines. Those need a proper repair, not just a mop. We replace failed condensate pumps and float switches and clear or repair the drain.
When you book an AC leak repair online, the problem is pre-filled for us, or call (760) 728-8716. More on our AC repair page and in our common AC problems guide. A yearly tune-up includes checking the condensate drain, which ENERGY STAR notes can cause water damage when plugged.
“Jack is always quick to fix the problem!”
Frequently asked questions
Why is my AC leaking water inside the house?
Most often the condensate drain line is clogged with algae, sludge or debris, so water backs up and overflows the drain pan. Other causes are a cracked or rusted pan, a failed condensate pump, or a frozen coil that's thawing. Turn the AC off, wipe up the water, and check the drain before restarting.
Is it safe to run my AC if it's leaking water?
It's best not to. Running it keeps producing water that has nowhere to go, which can damage floors, drywall and ceilings and encourage mold. Turn the system off at the thermostat, and switch it off at the breaker if water is near wiring. Once the drain is clear and the pan is dry, try again.
What is an AC float switch?
A float switch is a small safety device in the drain pan or drain line. When water rises because the drain is blocked, the float lifts and cuts power to the AC so the pan doesn't overflow. If your AC suddenly won't cool and the pan is full, a tripped float switch is the likely reason.
Should I worry about a water stain on the ceiling under my AC?
Yes. A stain below an attic air handler usually means the drain or overflow pan has been leaking for a while. Turn the AC off, photograph the stain, and have the system checked soon. EPA advises drying water-damaged materials within 24 to 48 hours to help prevent mold growth.