Water around your indoor AC unit sends most homeowners straight to a $150+ service call. Sometimes that's exactly right. But the single most common cause is a clogged condensate drain — and preventing it costs about twenty bucks a year. Here's how to tell the difference, from people who work on these systems.
Why your AC makes water in the first place
Your AC doesn't just cool air — it wrings moisture out of it. That water collects on the evaporator coil, drips into a drain pan, and flows outside through the condensate drain line. In a humid climate, that's gallons a week moving through a small pipe.
Cause #1: a clogged drain line
That pipe is dark, wet, and warm — perfect for algae and slime growth. Over a season or two, the growth narrows the line until it blocks. The pan fills, overflows, and you get water on the floor, a stained ceiling if the unit is in the attic, or a system that shuts itself off if it has a safety float switch. This is the cause behind most residential AC leaks, and it's the most preventable one.
Other causes worth knowing
- A frozen coil that thawed — usually from a badly clogged filter starving the coil of airflow. Ice melts faster than the drain can carry it away.
- A cracked or rusted drain pan — common on older units; this one needs a technician.
- Low refrigerant — also freezes the coil. If your system is icing up repeatedly, that's a pro call, not a DIY fix.
Call a technician if: the leak keeps coming back after the drain is cleared, you see ice on the lines, the pan is visibly damaged, or the unit is in an attic above finished ceilings and actively dripping. Water damage gets expensive faster than service calls do.
The $20-a-year prevention
Condensate drain tablets sit in the pan and dissolve slowly, stopping algae and slime before they can build the clog. One tablet a month during cooling season is the whole routine — drop it in near the drain opening and forget it. Our Drain Protection Tablets are $20.99 for a 30-count bottle (and there's a Subscribe & Save option — every 6 months, 15% off). Compare that to one emergency call, or one ceiling repair.
Two more cheap layers of insurance:
- A WiFi Leak Alarm ($39.99) — set it by the unit; your phone hears the drip before your ceiling does.
- A Drain Line Flush Kit ($25.49) — clears an existing slow drain before it becomes a full blockage.
And the simplest layer of all: filters ship free with a bottle of tablets on your first Filter Plan delivery — because the two most common AC problems, dirty filters and clogged drains, are both just maintenance that somebody forgot. We'd rather you never need the service call.