Why is my AC leaking water inside my house in Atlanta?

Where The Water Starts

An AC unit cools air by pulling humidity out of it, and that moisture collects as liquid water on the evaporator coil. In Atlanta's humid summers, that coil produces a steady drip for hours at a time. The water is supposed to fall into a drain pan underneath the coil, then leave through a condensate line, usually PVC, that carries it outside or into a floor drain. When any part of that path fails, the water has nowhere to go but down into the house.

Attic-mounted AC units are common in Atlanta, from ranch-era homes to newer builds near Buckhead and Sandy Springs, and that placement is exactly why a leak goes unnoticed so long. Nobody walks the attic daily to check the drain pan or the condensate line. Algae builds quietly inside the pvc line, the float switch fails to trip, and water works into insulation and ductwork above a bedroom ceiling for days before a stain finally shows through the drywall.

The Clogged Line

The condensate line is narrow, and algae grows easily inside a dark, constantly damp PVC pipe. Over a humid Atlanta summer, that algae builds into a slick coating and eventually a full clog. Once the line is blocked, condensate has nowhere to drain, so it backs up toward the coil and the pan instead. This is the single most common reason an AC unit leaks water inside, and it is also the easiest to prevent with a line that gets vacuumed out on a normal service schedule.

The drain pan is the backup plan for exactly this situation, and it is usually where the failure becomes visible. A pan that is cracked, rusted through, or simply too small for the amount of condensate a hard-running Atlanta unit produces in August will overflow onto the floor, the ceiling, or the ductwork below it. Some systems add a float switch that shuts the unit off when the pan fills too high, and a unit that keeps shutting off on its own is often telling you the pan is already overwhelmed.

What Makes It Worse

Sweating ductwork gets mistaken for a leaking AC unit fairly often. When humid air meets a cold duct surface, condensation forms on the outside of the metal, and if the duct's insulation is thin, worn, or missing in a spot, that condensation drips just like a real leak would. This shows up most in older housing stock, including parts of the city where original ductwork has never been reinsulated, and it needs a different fix than a clogged line does.

A unit that is oversized or undersized for the house it's cooling also runs into leak problems, because it either short-cycles and never removes humidity properly or runs so long that it produces more condensate than the pan and line were built to handle. Either way, the visible symptom is the same water stain or the same drip, which is why matching the actual cause to the actual fix matters more than guessing based on what the last house had.