Why Is My AC Leaking Water Inside?

If you've found a puddle under your indoor AC unit, act quickly — water damage to drywall, flooring, and framing adds up fast. AC leaks inside the house are one of the most common service calls in Austin, especially during our humid summers. Most of the time the cause is straightforward, but ignoring it leads to mold and expensive repairs.

Key Takeaways

A clogged condensate drain line causes about 80% of indoor AC water leaks — you can often clear it yourself with distilled white vinegar or a wet/dry vacuum.
Turn the AC off immediately when you see water pooling; mold can start growing within 24-48 hours of a leak.
Drain line clearing typically costs $75-$200 if you call a pro; drain pan replacement runs $250-$600 and costs more for attic installations.
Austin's humidity makes condensate drain clogs especially common — schedule drain line maintenance at the start of each cooling season to prevent leaks.

Possible Causes

Clogged condensate drain line DIY Fix

This is the cause about 80% of the time. Your AC pulls moisture from the air, and that water drains through a PVC pipe. Austin's humidity and warm temperatures create the perfect environment for algae and mold to grow inside the drain line, eventually blocking it. When the line clogs, water backs up into the drain pan and overflows.

Cracked or rusted drain pan Call a Pro

The drain pan sits under the evaporator coil to catch condensation. In older systems (10+ years), the pan can rust through or crack, allowing water to drip straight through. Secondary drain pans in the attic are especially vulnerable in Austin homes due to temperature extremes.

Frozen evaporator coil thawing Call a Pro

If the evaporator coil freezes (from low refrigerant or restricted airflow), ice builds up on the coil. When the system cycles off or you turn it off, all that ice melts at once — producing far more water than the drain pan can handle.

Disconnected or damaged drain line Call a Pro

Drain lines can come loose from vibration, or they can crack from age or UV exposure (for outdoor sections). If the fitting has separated, water will drip before it reaches the drainage point.

What to Do Right Now

Turn the AC system off immediately to stop producing additional condensation.
Soak up standing water with towels and place a container under the drip to catch any remaining water.
Locate the condensate drain line exit outside your home — it's typically a PVC pipe near the outdoor unit. Check if water is flowing out. If not, the line is likely clogged.
If you're comfortable, try flushing the drain line with a cup of distilled white vinegar poured into the access point near the indoor unit.
Call for service if the leak continues after clearing the drain, or if you see ice on the indoor coils.

Get Same-Day Help From a Licensed Contractor

Frequently Asked Questions

Why is my AC dripping water inside the house?

The most common cause in Austin is a clogged condensate drain line. Our humid climate promotes algae growth inside the drain pipe. When the pipe blocks, water backs up and overflows from the drain pan into your home.

Is a leaking AC an emergency?

It's not a safety emergency, but it is urgent. Water from a leaking AC can cause mold growth within 24–48 hours, damage drywall and ceiling materials, and ruin flooring. Turn the system off and address it the same day.

How do I unclog my AC drain line myself?

Locate the drain line access point (usually a T-shaped PVC fitting near the indoor unit). Pour one cup of distilled white vinegar into the opening. Wait 30 minutes, then check the outdoor drain exit for water flow. For stubborn clogs, a wet/dry vacuum on the outdoor end can pull the blockage out.

How much does it cost to fix an AC water leak in Austin?

A drain line clearing typically costs $75–$200. If the drain pan needs replacement, expect $250–$600 depending on the unit and accessibility (attic installations cost more). Evaporator coil issues that caused freezing and subsequent leaking can run $300–$1,500+.