AC Leaking Water Inside the House: Drain Line & Drain Pan Repair
AC leaking water inside the house? Clogged condensate drain line is Houston's #1 cause. What to do now, what it costs, and when it is an emergency.
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Quick answer: an AC leaking water inside is almost always a condensate problem — a clogged drain line, a full drain pan or a failed condensate pump. Your system pulls gallons of water out of Houston's humid air daily, and when the drain path blocks, that water goes into your ceiling or closet floor. Turn the system off at the thermostat, contain the water, and call +1 (254) 256-1678. Drain line clearing typically costs $75–$250.
Why this is Houston's most common AC problem
Air conditioners dehumidify as they cool: warm humid air passes over the cold evaporator coil, and moisture condenses out — exactly like water beading on a cold glass. In Houston, where relative humidity sits above 70% for much of the year, a residential system can produce several gallons of condensate per day. All of it has to leave through a ¾-inch drain line. Algae and slime thrive in that constantly wet, dark, warm tube, and the clog builds until the water has nowhere to go. Add the fact that most Houston air handlers sit in the attic directly above your ceilings, and a $150 maintenance item becomes drywall repair and mold remediation when ignored.
The causes, from most to least common
1. Clogged condensate drain line
Algae and sediment block the line; water backs up into the pan and overflows. The professional fix is clearing the line with vacuum or pressure and flushing it — $75–$250. Pouring a cup of distilled vinegar down the drain access every few months slows algae regrowth; it does not clear an existing clog.
2. Rusted or cracked drain pan
The metal pan under the coil corrodes over years — faster in Houston's humidity. Small pans can sometimes be repaired; usually replacement at $250–$700 is the lasting fix. A pan that has already overflowed into the ceiling may also mean wet insulation that needs attention.
3. Failed condensate pump
Where the air handler cannot drain by gravity (closets, interior installs), a small pump lifts the water out. Pumps fail every few years; replacement is quick and inexpensive compared to the water damage a dead pump causes.
4. Frozen coil thawing
A coil that froze from low refrigerant or bad airflow holds pounds of ice. When it thaws, that water overwhelms the drain — the puddle appears hours after the real problem started. If you saw ice before the water, the drain is innocent; the root cause is on the not-cooling list.
5. Disconnected or poorly sloped drain line
After attic work by other trades, drain lines get knocked loose or left without proper slope. Water pools, then spills. A simple reconnection and re-grading solves it.
What to do right now
- Turn the system off at the thermostat. Every minute it runs adds more condensate.
- Contain the water: buckets, towels, move furniture and electronics.
- If water is inside a ceiling, a small hole poked in the bulge with a bucket under it prevents a collapse — ugly but controlled.
- Do not cut power at random breakers unless water is near outlets or the air handler's electrics — then kill that circuit and stay clear.
- Call +1 (254) 256-1678. Say there is active water; drainage calls with overflow get priority scheduling.
What it costs in Houston
| Repair | Typical Houston range |
|---|---|
| Drain line clearing and flush | $75–$250 |
| Drain pan replacement | $250–$700 |
| Condensate pump replacement | $250–$700 |
| Float switch install (prevention) | $100–$200 |
If your system does not have a float switch, adding one during the repair is cheap insurance against a repeat. More ranges on the cost page; related service: AC unit repair.
Frequently asked questions
Why is my AC leaking water inside the house?
The number one cause in Houston is a clogged condensate drain line: your AC pulls gallons of water out of humid air every day, algae clogs the drain, and the water overflows the drain pan. Other causes: a rusted or cracked drain pan, a failed condensate pump, a frozen coil thawing, or a disconnected drain line. If water is coming through a ceiling, turn the system off and call.
Is water dripping from my AC dangerous?
The water itself is just condensate, but where it goes is the problem: attic air handlers overflow into ceilings and walls, causing drywall damage and mold — which grows fast in Houston's humidity. Treat active leaking as urgent: off at the thermostat, buckets and towels down, then call.
How much does it cost to fix a clogged AC drain line?
Clearing a condensate drain line in Houston typically costs $75–$250. Replacing a rusted drain pan runs $250–$700. A condensate pump replacement is similar. If the float switch did its job and shut the system down before overflow, the repair is usually just the line clearing.
What is the float switch and why did my AC shut off?
The float switch is a small safety device in the drain pan or line that shuts the system off when water backs up — preventing ceiling damage. If your AC "died" on a humid day and the thermostat is blank or the system is dead, a tripped float switch is a real possibility. The fix is clearing the drain; the switch saved your ceiling.
How do I tell a water leak from a refrigerant leak?
Water leaks mean puddles, drips, ceiling stains and a system that still cools. Refrigerant leaks mean warm air, ice on the lines, hissing and weak cooling — refrigerant itself evaporates and never leaves a puddle. Oily residue at a fitting points to refrigerant; a plain water puddle under the air handler points to drainage.
Need AC repair today?
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