Clogged AC Drain Lines: Why They Happen and What to Do
In Sarasota's humidity, your AC removes a lot of water from the air every day. When the drain line clogs, that water backs up, sometimes into the ceiling.
Request an AC technicianHow it works
Water drips from the indoor coil into a pan and flows out through a drain line, often to the outside near the foundation.
Why lines clog
Warm, damp conditions are perfect for algae and slime, which build up inside the pipe along with dust. Lines with little slope or long runs clog faster.
Warning signs
Water around the air handler, a wet or stained ceiling below an attic unit, a musty smell, or an AC that shuts off unexpectedly.
Float switches
A safety switch in the pan or line turns the AC off when water rises. It's doing its job; the clog still needs clearing.
First steps
Turn the AC off at the thermostat, soak up water, and protect anything below. Check that the outside end of the line isn't blocked by mulch, soil or plants.
Prevention
Regular flushing and treatment during maintenance slows algae growth. Some homeowners add a treatment between visits; ask your technician what's suitable.
Secondary pans
Attic units should have a secondary pan with its own drain or switch. If you find water in it, the main drain is likely clogged.
Get it cleared
See drain line and leak repair.
Where the line ends
Find where your drain line comes out of the house, often a short white pipe near the outdoor unit or the foundation. If it's buried in mulch or blocked by soil, water can't escape. Keeping the end clear is an easy job you can do yourself.
Repeated clogs
If a line clogs every few months, it may have too little slope, a sag where water sits, or no trap where one is needed. A technician can re-run or adjust it.
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