Why Is My AC Leaking Water Inside My Home?

Stepping into a puddle of water on your floor is one of the most unsettling things a homeowner can discover; especially when it's coming from the air conditioner that's supposed to be keeping you cool, not soaking your carpet. If you've searched "AC leaking water inside your house" because you're staring at a mystery puddle right now, you're not alone. It's one of the most common service calls we get at Air Logic during Columbia, SC's hot, humid summers, and in almost every case, the fix is more straightforward than it looks.

How Your AC Is Supposed to Handle Water in the First Place

Before we get into what's going wrong, it helps to understand what your air conditioner is supposed to be doing with all that water. Your AC doesn't just cool the air in your home; it also pulls moisture out of it, which is a big deal in Columbia's muggy summers. As warm, humid air passes over the evaporator coil inside your indoor unit, the refrigerant inside the coil absorbs heat and causes water vapor in the air to condense on the coil's surface, much like condensation forming on a cold glass of sweet tea on a July afternoon.

That condensation drips into a drain pan beneath the coil, then flows out through a condensate drain line - typically a white PVC pipe - and exits your home safely, usually near your outdoor unit or into a floor drain. When every part of that system is working correctly, you'd never even notice it happening. When one part fails, that water has nowhere to go but onto your floor, ceiling, or walls.

Top Causes of an AC Leaking Water Inside Your House

Once we're on-site, our technicians typically trace an indoor water leak back to one of these seven issues:

• ‍Clogged Condensate Drain Line: this is the single most common cause of an AC leaking water inside a home. Dust, dirt, sludge, and algae build up inside the PVC drain line over time, especially in Columbia's humidity, and eventually block it completely. With nowhere else to go, condensate backs up into the drain pan and overflows into your home.‍
• Dirty Air Filter: a clogged filter restricts airflow across the evaporator coil. Reduced airflow drops the coil's temperature low enough that condensation freezes onto it instead of draining away, setting up the next problem on this list.‍
• Frozen Evaporator Coil: whether caused by a dirty filter, low refrigerant, or blocked return vents, a frozen coil eventually thaws - and when it does, it can release far more water than your drain pan and line were built to handle at once, causing a sudden indoor leak.‍
• Cracked or Rusted Drain Pan: on older systems, especially units past the 10–15 year mark, the metal or plastic drain pan beneath the coil can corrode, crack, or develop pinhole leaks. Once that happens, water leaks straight through the pan rather than being channeled into the drain line.‍
• Broken Condensate Pump: if your air handler is located in a basement, attic, or another spot below the drain line's exit point, your system likely relies on a small condensate pump to push water out. When the pump's motor fails or its float switch sticks, water has nowhere to go but back into your home.‍
• Low Refrigerant Levels: low refrigerant can cause the evaporator coil to run too cold, freezing condensation onto the coil instead of letting it drain normally. When the ice eventually melts, it can overwhelm the drain pan just like a frozen coil from a dirty filter.

Improperly Installed or Sloped Drain Line: condensate drain lines rely on gravity. If the line was installed without the correct slope, or if a section has sagged or come loose over time, water can pool inside the line instead of draining outside.

Why Columbia's Climate Makes This Problem Worse

Homeowners across Columbia, SC deal with this issue more than most because of how much moisture our summers pack into the air. High humidity means your AC's evaporator coil is pulling significantly more water out of your indoor air than it would in a drier climate, which puts extra strain on the condensate drain line and drain pan for months at a time. That's why AC leaking water inside your house tends to spike as a service call in the Midlands from late spring through early fall, exactly when your system is working its hardest and can least afford downtime.

Is a Leaking AC Actually Dangerous?

A small puddle might not seem urgent, but an indoor AC leak can cause real damage the longer it's ignored:

• ‍Water damage: standing water can warp flooring, stain ceilings and drywall, and damage furniture, insulation, and personal belongings.‍
• Mold and mildew growth: indoor water leaks left unaddressed for as little as 24 to 48 hours can create the damp conditions mold needs to take hold, which can affect indoor air quality and your family's health.‍
• Electrical hazards: water near your air handler, ductwork, or electrical components can create a shock or short-circuit risk.‍
• Further system damage: continuing to run a leaking AC can cause components like the blower motor or circuit board to fail, turning a simple repair into a much more expensive one.

What to Do the Moment You Spot a Leak

• Turn off your AC at the thermostat to stop additional water from being produced and prevent further damage.
• Soak up standing water with towels and move any furniture, electronics, or boxes out of the affected area.
• Check your air filter; if it's visibly dirty, that alone may be contributing to the problem.
• Locate the drain line near your outdoor unit and check for obvious blockages or disconnections, but avoid taking the system apart yourself.
• Call a licensed HVAC technician to diagnose the exact cause and repair it correctly the first time.

When to Call an AC Repair Professional

A little water around your indoor unit during peak humidity can sometimes be normal condensation. But you should call a professional right away if you notice standing water pooling on the floor, water stains spreading across a ceiling or wall, ice forming on your refrigerant lines or coil, your system running but failing to cool effectively, or a musty smell developing near your air handler. Trying to guess at the cause or ignoring it and hoping it dries up usually costs homeowners more in the long run than an upfront diagnostic visit.

How Air Logic Diagnoses and Fixes AC Water Leaks in Columbia, SC

Air Logic has been serving Columbia and the Midlands with AC repair services for more than 30 years, and an AC leaking water inside your house is one of the calls our technicians handle most often, especially during our hottest months. When you call us, we don't just mop up the symptom, we track down the actual cause.

Because water damage doesn't wait for regular business hours, our team is available 24/7 for emergency AC repair across Columbia, SC. Whether your leak turns out to be a simple drain line flush or a more involved repair like a coil or drain pan replacement, we'll walk you through the diagnosis, the repair, and the maintenance steps that keep the problem from coming back.