AC Tips

AC Leaking Water Inside? It’s Usually a Clogged Drain Line

By Sunny Coast AC team · November 5, 2026

Water on the floor by your AC closet? A wet spot on the ceiling? Most of the time, the cause is simple: a clogged drain line.

It was the #1 problem our team fixed in 2025 and 2026. About 1 in 5 of the AC jobs we finished came down to a clogged drain line.

Two buckets under an indoor AC unit to catch water from a leak — In a Kendall home, buckets were catching water under the indoor unit. The drain line was clogged.

Why your AC makes water

Your AC does two jobs. It cools the air, and it pulls water out of it. Miami air is full of water, so your AC can pull out several gallons on a hot day.

That water drips into a pan under the indoor unit. Then it flows out of your home through a small pipe called the drain line. Some homes also have a small pump that pushes the water out.

Why the drain line clogs

The drain line stays warm and wet all the time. That is the perfect place for algae and slime to grow. Dust and dirt stick to it, too.

Little by little, the slime builds up until the water can’t get through. The water backs up, fills the pan, and spills over.

A cut piece of AC drain pipe packed with slime — What we found inside a clogged drain pipe in a Weston home. The water had nowhere to go.

Signs your drain line is clogged

Water on the floor around the indoor unit or in the AC closet
A water stain on the ceiling under the AC (if your unit is in the attic)
Your AC shuts off by itself and won’t come back on
A musty smell near the unit
No water dripping from the drain pipe outside while the AC runs on a hot day

Why would the AC shut off? Many systems have a small safety switch. When the water gets too high, the switch turns the AC off so it doesn’t flood your home. It is doing its job.

Safety first.

Don’t open the unit, bypass the safety switch, or use a wet-dry vac near the wiring. Water and electricity don’t mix. If water is near an outlet or the ceiling is sagging, stay away from that spot and call us.

What you can safely do right now

Turn the AC off at the thermostat. This stops more water from coming.
Soak up the water. Use towels, or set a bucket under the drip.
Move things away. Keep boxes, rugs, and furniture away from the wet spot.
Check your air filter. If it is gray and dusty, change it. A dirty filter lets more dirt reach the drain.

That’s it. The rest is a job for a pro.

What we do when we come out

Every AC repair visit starts with a diagnostic visit, and it’s $0 to come out. It includes our 18-point check. You only pay for the work you approve. For a leak, we:

Find where the water is coming from (it isn’t always the drain)
Clear the clog and flush the drain line
Clean the drain pan and check it for rust or cracks
Test the safety switch
Make sure the water drains outside the way it should

Before and after: an AC drain pan full of sludge, then the same pan cleaned — In a Miami home, the drain pan under the coil was full of sludge (left). The same pan after we cleaned it and flushed the drain line (right).

We show you what we found and give you a flat price in writing before any work. Decide not to repair? You owe nothing for the visit.

AC drain pump tray full of algae sludge, before cleaning — Miami: the drain pump tray was full of algae sludge. Before and after we cleaned it and flushed the drain line.

The same drain pump tray after cleaning — Miami: the drain pump tray was full of algae sludge. Before and after we cleaned it and flushed the drain line.

How to keep it from coming back

Two easy things you can do yourself:

Change your air filter every 1 to 3 months. A clean filter means less dirt reaches the drain.
Do a vinegar flush about once a month. Pour 1 cup of white vinegar into your drain line’s access port. That is usually a short white pipe with a cap, near your indoor unit. The vinegar helps stop algae from growing back.

Before you pour: turn the AC off at the thermostat. Only do this when the drain is working. If water is already backing up, vinegar won’t clear it, so call us. Never mix vinegar with bleach or other cleaners.

Can’t find the access port? Ask our tech at your next visit, and we’ll show you.

Then, once a year, get a maintenance visit. We flush the drain line and clean the pan as part of it. And don’t ignore a small drip. It only gets worse.

See what our maintenance visit covers →

Water around your AC right now? Call or text us. We’ll walk you through it.

Call (786) 822-6861

Job counts from our team’s records, as of November 5, 2026.