AC Leaking Water Inside the House: Causes and Solutions

If your AC is leaking water inside the house, the problem is usually a clogged drain line, a frozen evaporator coil, or a damaged drain pan. This guide walks you through each cause in order, starting with the easiest and safest checks.

This post is part of the Air Conditioning troubleshooting silo. For the complete cooling guide, see the pillar post:
Air Conditioner Not Cooling? The Complete Troubleshooting Guide

1. Turn Off the AC to Prevent Damage

Water leaks can damage floors, walls, and ceilings. Shut the system down before inspecting anything.

Set the thermostat to Off.
Do not run the system until the cause is identified.

2. Check for a Clogged Condensate Drain Line

This is the most common cause of water leaks inside the home.

Locate the PVC drain line near the indoor unit.
Check for standing water in the drain pan.
If the line is clogged, water will overflow into your home.

How to clear the drain line:

Use a wet/dry vacuum on the outside drain line.
Remove debris or sludge from the pipe.
Flush with warm water if needed.

3. Inspect the Drain Pan for Cracks or Rust

The drain pan sits under the evaporator coil and collects condensation. If it’s cracked or rusted through, water will leak inside.

Turn off power at the breaker.
Remove the access panel.
Inspect the drain pan with a flashlight.

If the pan is damaged, it must be replaced by a technician.

4. Check for a Frozen Evaporator Coil

A frozen coil will melt and overflow the drain pan, causing water leaks.

Look for ice on the refrigerant lines.
Check for frost on the coil behind the access panel.
Turn the fan to On to thaw the coil.

For a full freezing guide, see:
AC Freezing Up: Why It Happens and How to Fix It

5. Replace the Air Filter

A dirty air filter restricts airflow and can cause the coil to freeze, leading to water leaks.

Locate the return air filter.
Remove and inspect it.
If dirty, replace it immediately.

6. Check the Condensate Pump (If Installed)

Some systems use a condensate pump to move water out of the home. If the pump fails, water will back up and leak.

Listen for the pump running.
Check for standing water around the pump.
Ensure the pump is plugged in and receiving power.

If the pump is dead, it must be replaced.

7. Inspect the Air Handler for Improper Installation

If the air handler is not level, water may spill over the drain pan.

Use a level to check the unit.
Ensure the unit is slightly tilted toward the drain line.

8. Check for Low Refrigerant Levels

Low refrigerant can cause the coil to freeze, which leads to water leaks when the ice melts.

Look for ice returning after thawing.
Listen for hissing sounds near the refrigerant lines.

Important: Only licensed HVAC technicians can handle refrigerant.

When to Call a Professional

Call an HVAC technician if you notice:

Repeated water leaks
Standing water in the drain pan
Frozen coil after replacing the filter
Cracked or rusted drain pan
Low refrigerant symptoms