Problem guide
Air conditioner leaking water
An AC makes water every hour it runs. A leak means that water is not getting to the drain.
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Written by HYRE HVAC Research Desk Primary-source research, data analysis and fact checking
The short answer
An air conditioner leaking water usually has a clogged condensate drain line, a full or cracked drain pan, a frozen evaporator coil that is thawing, a failed condensate pump, or a disconnected drain. Turn the system off to stop more water, protect the floor or ceiling, and check the filter.
Clearing a blocked drain at the cleanout is often within reach; a cracked pan, a pump failure or a recurring freeze needs a technician.
Do this now
This stops new condensate. If water is near electrical parts or outlets, switch off the breaker for the indoor unit too.
Towels, a bucket, and move belongings. For a ceiling stain under an attic unit, catch the drip and keep people away if the ceiling bulges.
Pull the filter. If you cannot see light through it, replace it. A clogged filter starves the system of airflow. ENERGY STAR suggests checking it monthly in heavy-use seasons.
Where the water comes from
| What you see | Likely cause | Who fixes it |
|---|---|---|
| Water around the furnace or air handler | Clogged condensate drain | Often you, at the cleanout; recurring: technician |
| Water after ice melts | Frozen coil from low airflow or low refrigerant | Filter: you. Refrigerant: technician |
| Pan full, AC shut off | Float switch doing its job; drain blocked | Clear the drain; technician if unsure |
| Water dripping from a pump | Failed condensate pump | Technician |
| Ceiling stain under attic unit | Overflowing or rusted secondary pan | Technician |
| Water dripping outside by the house | Normal drain outlet | Nothing to fix |
Clearing a clogged drain line
Many systems have a T-shaped cleanout with a cap on the drain line near the indoor unit. With the system off, you can remove the cap and flush the line with a cup of warm water to see whether it drains.
A wet-dry vacuum on the outdoor end of the drain can pull a clog out. Some manufacturers and contractors suggest a small amount of distilled vinegar in the cleanout to discourage algae; check your equipment manual first, and never mix cleaning chemicals.
If water does not flow, the clog is deeper, or the line was installed without enough slope, call a technician. ENERGY STAR’s maintenance checklist lists checking the condensate drain as contractor work, because a plugged drain can cause water damage and affect indoor humidity.
When to stop and call
Do not open the outdoor unit, furnace cabinet or control box. Capacitors can hold a dangerous charge with the power off, and line-voltage work is for a licensed technician.
Adding refrigerant, finding leaks or even attaching gauges requires EPA Section 608 certification.
Keep the system off and call.
Recurring ice points to low refrigerant or an airflow fault. See AC unit freezing up.
A pan replacement means working inside the unit.
What a technician will do
They will clear and flush the drain, check its slope and trap, test the float switch and any condensate pump, inspect the primary and secondary pans, and check why the coil froze if it did. On attic units, a secondary pan with its own float switch is a common safeguard.
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Questions
Why is my AC leaking water inside?
Is it safe to run my AC if it is leaking water?
How do I unclog my AC drain line?
Can low refrigerant cause water leaks?
Why does my AC drip outside?
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HYRE HVAC Research Desk
Primary-source research, data analysis and fact checking
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