Why Is My AC Leaking Water? The Gulf Coast Condensate Problem

Cooling and dehumidifying are the same act: warm, moist air crosses the cold evaporator coil, and its moisture condenses out — exactly like a cold glass sweating on a porch in July. In our climate that can mean 5–20+ gallons per day flowing into the drain pan and out the condensate line. Inland, dry-climate systems produce a fraction of that, which is why drain problems dominate service calls here in Dickinson, League City, and Galveston but barely register in El Paso.

Algae and biofilm. The drain line is dark, wet, and warm — a perfect greenhouse. Slime builds on the pipe walls until the line chokes, water backs into the primary pan, and then overflows into the secondary (emergency) pan if you have one, or onto your ceiling if you don't.

• Water stain on the ceiling below the attic unit — the classic Gulf Coast symptom. Treat it as urgent.
• Water at the base of a closet air handler — same problem, easier to spot early.
• AC shutting itself off — many systems have a float switch that kills cooling when the pan fills. Annoying, but it just saved your ceiling.
• Musty smell near the unit — standing water in the pan is also a mold farm; see why your house smells musty.

Often, yes. Find the drain line's exit point outside (a small PVC pipe near the outdoor unit, usually dripping when the AC runs). A wet/dry vacuum sealed over that outlet for a minute or two will pull most algae plugs through. Some homeowners pour a cup of distilled vinegar into the drain access tee near the indoor unit monthly during cooling season — a legitimate preventive habit.

Call a professional if the clog won't clear, if water has already reached drywall, or if the drain pan itself is rusted through (common on older systems — the pan is replaceable, but it's inside the unit). During every tune-up the Mackey Services team flushes the drain line and checks the float switch, because a $0 vinegar habit and an annual flush are dramatically cheaper than a ceiling repair.

Act same-day if water is actively dripping from a ceiling, if the leak continues with the system off (that may be a supply line, not condensate), or if the unit sits above living space with no working float switch. Water damage compounds by the hour, and in our humidity, wet drywall grows mold fast. If the system also stopped cooling, the float switch likely tripped — clearing the drain restores both.