Why your AC makes water
As warm, humid air passes over the cold indoor coil, moisture condenses, just like on a glass of iced tea. That water drips into a drain pan and flows out through a PVC condensate line, usually to the outside or into a household drain. In the Lake Houston area's humidity, that line runs nearly nonstop from May through October.
The most common causes of a leak
- Clogged condensate drain line. Algae and sludge grow inside the line and block it. This is by far the most common cause.
- Full or cracked drain pan. Older metal pans rust through, and plastic pans can crack.
- Tripped or missing float switch. Many systems have a safety switch that shuts the AC off when the pan fills. If yours is missing or stuck, water overflows instead.
- Frozen evaporator coil. When ice on the coil melts, it can overwhelm the pan. A frozen coil usually means an airflow or refrigerant problem.
- Disconnected or sagging drain line, especially in attic installations.
What you can do right now
- Turn the system off at the thermostat to stop more water from forming.
- Soak up standing water and protect ceilings and floors below an attic unit.
- Find the drain line's outside outlet and check whether it's dripping. No drip during cooling season usually means a clog.
- Some lines have an access port near the indoor unit where a cup of distilled vinegar can help keep algae down between service visits.
When to call a pro
Call a licensed HVAC contractor if water keeps coming back, if the unit is in the attic (ceiling damage gets expensive fast), or if you see ice on the coil or lines. A technician can clear the line properly, check the pan and float switch, and find any underlying airflow problem. Schedule AC repair, and ask about adding drain line cleaning to your annual maintenance.