The short answer
Water near the indoor unit almost always means the condensate drain line is clogged and the pan is overflowing. Switch the system off, dry the area, and check the drain line and the float switch. A clog that keeps coming back needs the line cleared and the cause found.
Your AC pulls a lot of water out of the air — in a humid South Florida summer, gallons a day. That water drips off the indoor coil into a pan and leaves the house through a small pipe called the condensate drain line.
When that line clogs, the water has nowhere to go. It fills the pan, overflows into the closet, the attic or the ceiling below, and sometimes trips a safety switch that shuts the system off. Here is how to deal with it.
Step 1: Switch the system off and protect the area
Turn the thermostat to Off to stop producing more water. Move anything that can be damaged and soak up standing water with towels or a wet vacuum.
If water is coming through a ceiling, the unit is probably in the attic above it; a stain spreading on drywall needs attention before it weakens the ceiling.
Step 2: Find the drain line and the pan
At the indoor unit, look for a PVC pipe, usually ¾ inch, leaving the cabinet near the bottom. Many systems have a small access tee with a cap on that line. Under the unit there may be a secondary pan.
- Water in the secondary pan: the main drain is backing up
- Water in the primary pan inside the cabinet: the drain is clogged at its start
- Water outside the pan: a cracked pan or a line that came apart
Step 3: Check the float switch
Many systems have a float switch in the pan or on the drain line. When water rises, it cuts power to the AC so it stops making more water. If your system stopped cooling and there is water in the pan, the float switch may be doing its job.
Once the water is cleared, the switch resets by itself. If the system still does not start, the switch or its wiring needs checking.
Step 4: Clear a simple clog
Where the drain line exits outside the house, a wet vacuum held tightly over the end can often pull out the clog of algae and sludge. At the access tee inside, a cup of white vinegar poured slowly helps keep the line clear afterward.
Don't: pour bleach or drain cleaners meant for sinks into the line or the pan. They can damage the pan and the coil.
Step 5: Know when it is more than a clog
If the line clogs again within weeks, or water appears even though the line flows, something else is going on: a line without enough slope, a sagging section that holds water, a cracked pan, or a coil that freezes and then melts all at once.
An AC drain line repair visit looks at the whole path, from the pan to the outside, and at the float switch, so the water goes where it should go.
Step 6: Protect against the next overflow
A float switch is the simplest protection an attic or closet unit can have. It sits in the pan or on the drain line and shuts the system off before water spills over. If your system does not have one, ask about adding it.
- A float switch in the secondary pan or on the drain line
- A secondary pan under attic units, with its own drain or switch
- An access tee on the drain line so it can be flushed
- Enough slope on the line that water never sits in it
In condos, the indoor unit often sits in a closet over finished floors and above a neighbor's ceiling, so these details matter even more there.
What to tell us when you call
- Where the water is: closet, attic, ceiling below, around the cabinet
- Whether the system stopped cooling (a float switch may have tripped)
- Whether you see ice on the indoor coil or the copper lines
- Whether it has happened before and how often
- Whether the unit is in a condo closet, a garage or an attic
How to avoid it next time
In humid months the drain line grows algae and collects dust from the coil. Keeping it clear takes far less effort than repairing a stained ceiling.
- Pour a cup of white vinegar into the access tee every couple of months
- Change filters on schedule so less dust reaches the coil and the pan
- Include the drain line in a yearly tune-up
- If your unit is in an attic, make sure it has a float switch
Key takeaways
- Water at the indoor unit is usually a clogged condensate drain.
- Switch off, dry the area, then clear the line.
- A float switch that stops the system is protecting your home.
- A clog that returns quickly points to a slope, sag or pan problem.
Further reading
- Maintenance Checklist ENERGY STAR
- A Brief Guide to Mold, Moisture and Your Home U.S. Environmental Protection Agency
Questions
My AC stopped and there is water in the pan under it. Is it broken?
Probably not. A float switch likely sensed the water and cut power. Clear the drain, let the pan empty and the switch usually resets. If the system still does not start, the switch or wiring needs a look.
How often should the drain line be cleaned?
In South Florida, a quick vinegar treatment every couple of months and a full check once a year is a good rhythm. Systems in attics or with long drain runs may need more attention.
Can a dirty filter cause water leaks?
Yes, indirectly. A clogged filter can make the indoor coil freeze. When the ice melts, more water than the pan can handle comes off at once.
Water is dripping from my ceiling vent, not the unit. What does that mean?
Usually condensation forming on a duct or register in a humid attic, or a disconnected duct. That is more of a duct issue than a drain issue.