Do this first: If you see water dripping from your indoor unit or pooling on the floor, turn the thermostat to "off" (not just "fan only"). Running a system with a backed-up drain line can overflow the secondary pan and damage drywall or ceilings.

The 5 Most Common Causes

1. Clogged Condensate Drain Line

This is the cause roughly 80% of the time. As your AC cools air, it pulls humidity out — and that moisture drips into a drain pan and flows out through a PVC drain line. Over time, algae, mold, and debris build up in the line until it clogs and water backs up into the pan and overflows.

Oklahoma's heat means ACs run a lot in summer, pulling a ton of moisture and filling that drain line with algae fast. If you haven't had maintenance done recently, this is almost certainly your issue.

2. Frozen Evaporator Coil Thawing Out

If your AC was blowing warm air and is now leaking large amounts of water, you probably had a frozen coil. When the coil freezes over (usually from a dirty filter or low refrigerant), the ice melts the moment you turn the system off — dumping a lot of water into the drain pan at once. The drain pan can't handle that volume and overflows.

The fix isn't just clearing the drain — you need to find why the coil froze in the first place.

3. Dirty Air Filter

A clogged filter restricts airflow over the evaporator coil. Without enough warm air moving across it, the coil gets too cold and freezes. See cause #2 above for what happens next. Check your filter right now — if it's gray and dense, that's likely your problem.

4. Low Refrigerant

Low refrigerant drops the pressure in the system, which causes the evaporator coil to get colder than it should and freeze. If your system has a refrigerant leak, the coil will freeze repeatedly until the leak is found and repaired.

5. Cracked or Rusted Drain Pan

Older systems (10+ years) can develop cracks in the secondary drain pan. Water drains normally but the pan itself leaks. You'll usually see this as slow dripping from the bottom of the air handler rather than sudden overflow.

What You Can Try Right Now

1
Turn the system off at the thermostat to stop water flowing into the backed-up pan.
2
Check the air filter — if it's dirty, replace it. This solves frozen-coil issues and prevents them from coming back.
3
Try the condensate drain port — there's usually a cap on the drain line access port near your indoor unit. Remove it and pour about 1 cup of distilled white vinegar into the line. This dissolves algae and can clear a mild clog.
4
Wait 30 minutes, then check if water is draining normally before turning the system back on.

If the drain line is severely clogged, vinegar won't cut it. A technician uses a wet vac to pull the clog from the exterior drain outlet — it usually takes less than 15 minutes.

When to Call

Call us if: the drain line is still clogged after trying vinegar, you see the coil is iced over, you've replaced the filter and the problem keeps coming back, or you notice water stains on your ceiling or walls from the overflow.

Serving Oklahoma City, Edmond, and the OKC Metro

We clear drain lines, fix frozen coils, and find refrigerant leaks. Same-day service available.

Call (405) 281-4846

Frequently Asked Questions

Why is my AC dripping water inside the house?

The most common cause is a clogged condensate drain line. As your AC removes humidity, the water drains through a line that can clog with algae or debris. When it backs up, water overflows the drain pan and leaks into the house.

Is a leaking AC dangerous?

A dripping AC can cause drywall damage, mold growth, and ceiling stains if ignored. Turn the system off and call for service to prevent water damage to your home.

Can I fix an AC drain line clog myself?

You can try pouring distilled vinegar down the condensate drain access port to dissolve algae buildup. If that doesn't work within a few hours, a technician can use a wet vac to clear the line quickly.

Why is my AC unit freezing up and then leaking?

A frozen evaporator coil will melt when you turn the system off, dumping large amounts of water into the drain pan at once. This often overflows. The freezing is usually caused by restricted airflow (dirty filter) or low refrigerant.