An AC leaking water inside your house in Greenville SC almost always comes down to one of three things: a clogged condensate drain line, a frozen evaporator coil that melts and overflows the pan, or a failing drain pan itself. The water is condensation - the same moisture your system pulls out of humid Upstate air all summer - and it is supposed to leave through a drain, not across your floor. Below we walk through every cause we see on service calls, what you can safely check yourself, and when it is time to hand it off.
The short answer: why your AC leaks water inside
AC leaking water inside house Greenville SC is a drainage problem, not a cooling problem - the refrigerant loop is usually fine, but the water the coil produces has nowhere to go. Your air handler pulls warm, humid air across a cold evaporator coil. That coil sweats. In a Greenville summer, with relative humidity sitting in the 70s most afternoons, a 3-ton system can condense 15 to 20 gallons of water a day. All of it is supposed to run down a sloped drain line and out of your house.
When that path is blocked, pinched, frozen, or broken, the water backs up into the drain pan and spills over. That is the puddle you are seeing. The fix is almost never a new AC - it is restoring the drain path and stopping whatever caused the backup.
How a normal AC handles water (and where it goes wrong)
Every central system has four water-handling parts, and a leak means one of them failed.
- The evaporator coil - the cold part that condenses moisture out of your indoor air.
- The drain pan - a shallow tray under the coil that catches the drips.
- The primary drain line - a 3/4-inch PVC line that carries water to a floor drain, utility sink, or outside.
- The secondary pan and float switch - a backup pan and a safety switch that shuts the system off if the primary drain backs up.
When the primary line clogs, the secondary pan fills and the float switch should trip the system off. When that switch is missing, wired wrong, or stuck, the pan overflows instead. We find missing float switches on roughly one in four older systems we open up in Greenville.
The 6 most common causes of AC water leaks in Greenville
These are the six causes our technicians actually find on AC water leak inside Greenville calls, ranked by how often we see them.
1. A clogged condensate drain line
This is the number one cause, and it is not close. Upstate air carries pollen, dust, and - in older neighborhoods - a fine grit that mixes with the algae that grows inside a wet, dark drain line. Over 6 to 18 months that sludge forms a plug. Water backs up, the pan overflows, and you get a stain on the ceiling below the air handler.
If you have ever wondered why your AC drips water in Greenville only in the summer, this is usually it - the line is wet and warm, and algae grows fastest in July and August.
2. A frozen evaporator coil
A coil that drops below 32°F turns condensation into ice. The ice builds up, blocks airflow, and then melts all at once when the system cycles off - dumping more water than the pan can hold. Low refrigerant, a dirty air filter, or a weak blower motor all cause this. If you see frost on the copper lines or the coil, shut the system off and let it thaw before you do anything else.
3. A cracked or rusted drain pan
Drain pans are stamped steel or plastic. In a humid attic or closet, steel pans rust through in 8 to 12 years. Once the pan itself leaks, no amount of drain cleaning helps - the pan has to be replaced. We see this most often in homes built in the 1990s and early 2000s around residential AC repair Greenville SC service areas like Mauldin and Simpsonville.
4. A disconnected or improperly sloped drain line
Drain lines need about 1/4 inch of fall per foot. If a line was run flat, kinked, or pulled loose during a remodel, water pools in the low spot and eventually overflows. This is common after attic work or a new roof install - someone bumps the line and never notices.
5. A dirty air filter choking airflow
A clogged filter drops airflow across the coil, and the coil gets cold enough to freeze. That is the same failure mode as a refrigerant problem, and it costs $10 to fix. Change your filter every 30 to 60 days in Greenville's pollen season - March through May is the worst stretch.
6. A failed condensate pump
If your air handler sits in a basement or closet with no gravity drain, a small condensate pump pushes water up and out. When the pump fails or its reservoir clogs, water overflows the pan within a day. You will usually hear the pump running constantly or not at all.
What to do if your AC is leaking water right now
If your AC is leaking water in Greenville South Carolina right now, shut the system off at the thermostat first, then at the breaker if the leak is heavy. Water and live electrical components do not mix, and the air handler has a control board and a blower motor sitting inches from that pan.
- Kill the power at the thermostat and, if the leak is near the unit, the breaker.
- Protect the floor with towels or a shallow pan. Water under a wood floor or in a ceiling cavity causes thousands in damage fast.
- Find the air handler - attic, closet, or garage - and look at the drain pan. Is it full? Is the coil iced?
- Check the filter. A gray, matted filter is a strong clue the coil froze.
- Look at the drain line exit - the PVC stub outside or at a utility drain. If nothing is dripping while the system runs, the line is clogged.
If the pan is full and the coil is not iced, the drain is clogged. If the coil is iced, let it thaw for 2 to 4 hours with the fan on and the cooling off, then check again. If water is still pooling after that, stop and call us.
Common mistakes Greenville homeowners make with AC water leaks
The mistakes we see most often turn a $150 drain cleaning into a $1,200 repair. Avoid these.
- Running the system to "see if it clears." If the drain is clogged, running the AC just adds more water to an already-full pan.
- Pouring bleach down the drain line. It kills algae for a week and then corrodes the PVC and the pan. Use a shop vac or a proper drain-cleaning brush instead.
- Ignoring a slow drip. A drip today is a ceiling stain next month. Condensate damage is one of the most common insurance claims we hear about from Greenville homeowners.
- Replacing the whole system when the pan is the problem. A cracked pan is a $200 to $450 repair, not a $7,000 replacement.
- Letting a "handyman" recharge refrigerant. Refrigerant work requires EPA Section 608 certification. If the coil is freezing because of a refrigerant leak, that leak has to be found and repaired - not topped off.
When to call a professional for an AC water leak in Greenville
Call a professional when the pan refills after you clear the drain, when you see ice on the coil or copper lines, when the drain pan is cracked, or when water is coming through a ceiling. Those four situations need tools and parts you do not have on a Saturday afternoon.
Our team at Greenville AC Repair Pros handles AC drain line clog repair Greenville SC every week - we clear the line, flush the pan, test the float switch, and confirm the drain is flowing before we leave. If the coil is frozen because of a refrigerant issue, we find the leak and repair it rather than just adding Freon. And if your system is old enough that the pan is rusting through, we will tell you straight whether a pan replacement or a central AC repair Greenville SC makes more sense for your budget.
Homeowners in older mill-village neighborhoods like AC repair in Parkins Mill deal with a specific version of this - original 1950s drain lines that were never upsized for modern humidity loads. We see the same pattern in AC repair in West Greenville, where attic air handlers sit in 130°F summer heat and the pans rust faster than the rest of the house.
Frequently Asked Questions
Why is my AC leaking water inside my house in Greenville SC?
In 9 out of 10 cases it is a clogged condensate drain line. The coil still condenses 15 to 20 gallons of water a day, but the drain is plugged with algae and dust, so the pan overflows. A frozen coil or cracked pan causes the rest.
What causes AC water leaks in Greenville?
Greenville's summer humidity - often 70% or higher - is the root cause. That moisture feeds algae in drain lines, freezes coils when airflow is low, and rusts steel drain pans in 8 to 12 years. Pollen season adds to the clog.
How do I stop my AC from leaking water in Greenville?
Shut the system off, clear the drain line with a shop vac, change the filter, and let a frozen coil thaw for 2 to 4 hours. If the pan refills within a day, the clog is deeper than a homeowner can reach - call us at (903) 627-1334.
When should I call an AC pro for a water leak in Greenville?
Call when the pan refills after you clear the drain, when you see ice on the coil, when the pan is cracked, or when water is staining a ceiling. Those need a pro with a recovery machine and replacement parts on the truck.
Can a dirty filter cause an AC water leak?
Yes. A clogged filter drops airflow across the evaporator coil, and the coil drops below freezing. The ice melts all at once when the system cycles off, and the pan overflows. Change the filter every 30 to 60 days.
Get help with AC Repair in Greenville
If your AC is leaking water inside your Greenville home, we can be there today. We clear the drain, repair the coil or pan, and confirm the system is dry before we leave.
Call Greenville AC Repair Pros at (903) 627-1334 - same-day service across Greenville and the surrounding Upstate.