AC Leaking Water Inside? 7 Causes & How to Fix It

Finding a puddle of water around your indoor AC unit is alarming—and for good reason. Left unchecked, AC water leaks cause ceiling stains, warped flooring, drywall damage, and mold growth. But here's the reassuring news: the most common cause is a simple clogged drain line, and many homeowners can fix it themselves in under 30 minutes.

In this guide, we'll walk through exactly why your AC is leaking, how to stop the damage right now, and whether you're dealing with a quick DIY fix or something that needs a professional. Charlotte's high humidity means your AC removes a lot of moisture from the air every day—sometimes several gallons—so drainage problems are especially common here.

Why Your AC Produces Water (And Where It Should Go)

Understanding how water gets into your AC helps diagnose the leak. Your evaporator coil (inside the indoor unit) gets very cold as refrigerant flows through it. When warm, humid air from your home passes over this cold coil, moisture condenses on it—just like water droplets forming on a cold glass of iced tea.

That condensation drips into a drain pan below the coil, then flows through a PVC condensate drain line that routes the water outside your home or into a floor drain. In Charlotte's humid climate, your AC can remove 3-5 gallons of water per day during peak summer. When any part of this drainage system fails, that water has to go somewhere—and that somewhere is usually your floor, ceiling, or walls.

What to Do Right Now

Causes You Can Fix Yourself

1. Clogged Condensate Drain Line (Most Common)

This is the number one cause of AC water leaks—by a wide margin. Over time, algae, mold, dust, and debris build up inside the PVC drain line that carries condensation outside. Charlotte's humidity accelerates this growth. When the line clogs, water backs up into the drain pan, overflows, and leaks into your home.

2. Dirty Air Filter

A dirty filter restricts airflow over the evaporator coil, causing it to get too cold and ice up. When you turn the system off or the ice gets heavy enough, it melts—sometimes faster than the drain pan can handle—and water overflows. This is an indirect cause of water leaks, but it's extremely common and free to fix.

3. Overflowing Drain Pan

The drain pan sits directly under the evaporator coil to catch condensation. If the drain line is slow (partially clogged) or your AC is producing more condensation than usual on extremely humid days, the pan can overflow before the water drains fast enough. Check for standing water in the pan—it should be mostly empty when the drain line is working properly.

Causes That Need Professional Repair

4. Cracked or Rusted Drain Pan

If your AC system is 12-15+ years old, the metal drain pan may have developed rust holes or cracks from years of constant moisture exposure. Water falls right through the damaged pan instead of flowing to the drain line. You can spot this by looking underneath the pan for drips even when the drain line is clear.

Typical repair cost: $150-$350 for drain pan replacement. This is a straightforward repair, but the pan location inside the air handler makes it a professional job.

5. Frozen Evaporator Coil (Melting Ice)

When the evaporator coil freezes—from restricted airflow, low refrigerant, or a blower motor issue—a block of ice forms. When the system cycles off or the ice gets thick enough, it melts rapidly. That sudden rush of water overwhelms the drain pan and causes flooding. If you see ice on the coil or copper refrigerant lines, the water leak is a symptom of a deeper problem.

6. Low Refrigerant

Low refrigerant causes the evaporator coil to drop below freezing, creating ice that eventually melts and overflows. Unlike a clogged drain, this problem will keep coming back because the coil keeps freezing. Signs include reduced cooling performance, hissing sounds near the indoor unit, and ice forming on the copper lines.

Typical repair cost: $200-$800 for leak repair and recharge. The leak must be located and sealed before adding refrigerant—simply topping it off is a waste of money since it will leak out again.

7. Disconnected Drain Line or Failed Condensate Pump

Drain lines can work loose from connections over time, especially if they weren't properly secured during installation. The water flows out at the disconnected joint instead of reaching the exit point. Additionally, if your indoor unit is in a basement or low area, it relies on a condensate pump to push water upward to a drain. If that pump fails, water backs up immediately.

Typical repair cost: $100-$250 for reconnecting a drain line. Condensate pump replacement: $200-$400 including parts and labor.

AC Water Leak Repair Costs in Charlotte (2026)

Here's what you can expect to pay for the most common water leak repairs. Costs include parts and labor.

Real Customer Review

★★★★★

"Found water all over our utility room floor. Kodiak came out the same afternoon, cleared the drain line, and showed us how to maintain it ourselves going forward. Exactly the kind of honest service we needed."

How to Prevent AC Water Leaks

Most AC water leaks are entirely preventable with basic maintenance. Here's what we recommend, especially given Charlotte's high humidity:

When to Call a Professional

A clogged drain line is often a DIY fix. But call a professional immediately if:

• Water is leaking near electrical components or outlets
• You see ice on the evaporator coil or refrigerant lines
• The drain line clog returns quickly after clearing it
• Water is coming from inside the unit (not the drain pan)
• You notice mold growth around the unit or in the drain pan
• The leak has caused visible damage to walls, ceiling, or flooring
• Your system is 12+ years old and you suspect a cracked drain pan