AC Leaking Water Through the Ceiling? How to Tell an AC Drain Leak From a Plumbing Leak

Your air conditioner removes moisture from the air. That water drips into a pan and runs out through a small drain line. In many Arlington homes, the indoor AC unit sits in the attic, right above a ceiling. If the drain clogs or the pan rusts through, water can stain the ceiling below. A ceiling stain can also come from a water pipe, so it helps to know which one you have. If the water is not from the AC, call (817) 285-5426 for leak detection.

Why is my AC leaking water?

The most common cause is a clogged condensate drain line. Algae, dust and slime can build up inside it, so water backs up and overflows the pan. Other causes are a cracked or rusted drain pan, a drain line that came loose, or a frozen coil that drips more water than usual as it thaws.

• Clogged condensate drain line
• Rusted or cracked drain pan
• Loose or broken drain pipe
• Frozen coil that melts all at once
• Float switch that is missing or not working

How can I tell an AC leak from a plumbing leak?

Look at where and when the water shows up. An AC leak is usually right under or near the indoor unit and gets worse when the AC runs a lot. A plumbing leak often shows up near bathrooms, the kitchen or the water heater, and it continues even when the AC is off. A water meter test helps: if the meter moves with all water off, a pipe is leaking.

Our high water bill guide walks through the meter test step by step.

What should I do first?

Turn the AC off at the thermostat so it stops making water. Put a bucket or towels under the drip. If it is safe, look at the drain pan in the attic. A pan full of water points to a clog. If the pan is dry, the water may be coming from a pipe instead.

1. Turn off the AC at the thermostat.
2. Catch the water and move anything that can be damaged.
3. Check the AC drain pan if you can reach it safely.
4. Do a water meter test with all water off.
5. Call an HVAC company for the AC, or a leak detection pro if the meter moves.

Only walk on the attic joists or a solid walkway, never on the drywall between them.

Can a wet ceiling cause other problems?

Yes. Wet drywall can sag, stain and grow mold if it stays damp. Insulation above it can hold water for a long time. Dry the area fast and replace soaked material. If you are not sure where the water came from, a moisture meter and thermal camera can show how far it spread.

Read more about a water leak in a wall or ceiling and how leak detection works.

How much does leak detection cost in Arlington?

If the water turns out to be from a pipe, a basic leak detection visit in Arlington usually costs $150 to $400. AC drain repairs are handled by an HVAC company. You get our price before work starts.

General estimates for Arlington, TX in 2026. Your exact price is confirmed before any work begins.