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AC Leaking Water Inside
in Richardson, TX
Richardson's humid summers mean your AC pulls a surprising amount of water out of the air every day. That water is supposed to drain out through a small pipe called a condensate drain line. In the heavy heat and humidity of a North Texas July, algae and mold grow inside that drain line and block it within a single season, causing water to back up and overflow the drain pan.
Quick Answer
Your indoor AC unit collects moisture from the air and drains it away through a condensate drain line. When that line clogs, water backs up and spills out of the drain pan. A technician clears the line with a wet-vac or flush, which usually fixes the problem quickly. Don't ignore standing water near your air handler. Call (361) 202-9465 before it soaks the ceiling or floor.
Telltale Signs
Warning Signs to Watch For
- Water pooling on the floor around your indoor air handler
- Water stains on the ceiling below a second-floor air handler
- A musty or moldy smell coming from the vents or the air handler closet
- The AC shuts off on its own even though nothing seems wrong
- The drain pan under the unit is visibly full of standing water
Root Causes
What Causes AC Leaking Water Inside?
Clogged Condensate Drain Line
The condensate line is a small pipe, usually about three-quarters of an inch wide, that carries drain water outside or to a floor drain. Algae and mold grow inside it because it's dark and wet, and they can plug the line completely within one summer in Richardson's humid conditions. Once blocked, water fills the drain pan and overflows onto whatever is below it.
The Fix
Condensate Drain Line Cleaning
The technician uses a wet-vacuum on the end of the drain line and may flush it with a diluted bleach solution to kill algae. Adding a condensate treatment tablet every season helps keep the line clear between service visits.
Cracked or Rusted Drain Pan
The drain pan sits directly under the evaporator coil and catches condensation before it reaches the drain line. Over time, especially in systems that have been running for more than 15 years, the pan corrodes or cracks and lets water leak straight through. Homes in the Greenwood Hills area of Richardson that still have original 1980s equipment are a common place to find drain pans in poor shape.
The Fix
Drain Pan Replacement
A technician removes the old pan and installs a new one sized to fit the unit. In some cases a secondary pan with a float switch can be added as a backup to shut the system off before water spills.
Frozen Coil Thawing Rapidly
When a frozen evaporator coil melts, it releases a large amount of water all at once, far more than the drain system is built to handle quickly. That volume overwhelms the drain pan and the line, and water spills out. This happens after the airflow or refrigerant problems that caused the freeze are corrected, but before the drain system has a chance to catch up.
The Fix
Controlled Thaw and Drain Check
The system needs to thaw slowly with the fan set to run-only and the cooling turned off. A technician checks that the drain line is clear before the full thaw so the water has somewhere to go.
Self-Diagnosis
Which Cause Applies to You?
Check the signs you're observing to narrow down the likely root cause before your inspection.
| What You're Seeing | Clogged Condensate Drain Line | Cracked or Rusted Drain Pan | Frozen Coil Thawing Rapidly |
|---|---|---|---|
| Water overflows steadily even on days the AC runs normally | |||
| Water appears suddenly after the AC was iced over and then shut off | |||
| Rust-colored water in or around the drain pan | |||
| Musty smell from vents along with water pooling | |||
| AC shuts itself off due to a float switch tripping | |||
| Water only appears after a long run cycle in high humidity |
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