AC Leaking Water
A little water under the air handler looks harmless, which is exactly why it does so much damage - left alone through a humid San Antonio summer, that slow drip soaks drywall, warps flooring, stains ceilings, and grows mold inside walls and ductwork where you cannot see it. If the water reaches the electrical parts in the air handler, a cheap drain clog becomes a fried control board. Water is the one AC symptom where the damage compounds every day you ignore it.
Your AC does not just cool the air, it wrings moisture out of it. As humid indoor air passes over the cold evaporator coil, water condenses on the coil the same way it beads on a cold glass, then drips into a pan below and runs out through the condensate drain line. That is normal and constant, especially in San Antonio humidity - a working system can shed gallons a day. A leak almost always means that water has lost its escape route: the drain is blocked, the pan is compromised, or so much water is forming at once that the drain cannot keep up.
The most common cause - a condensate drain line clogged with algae and sludge - sits somewhere between quick fix and real repair. Some homeowners clear a visible drain opening or pull the clog from the outdoor end with a wet/dry vacuum, and that is a legitimate quick fix when it works. The real repairs are the ones a vacuum will not touch: a rusted-through or cracked drain pan, a failed condensate pump on systems that need one to lift water up and out, or a frozen coil dumping its meltwater all at once. If the pan keeps refilling after you clear the visible opening, the trouble is deeper.
Hard water is the quiet villain here. The Edwards Aquifer supply that serves most of the metro is mineral-rich, and as condensate evaporates it leaves scale that narrows and eventually plugs drain lines faster than you would see in a soft-water region. Our humidity makes it worse, because a system pulling heavy moisture from the air all summer produces the most condensate exactly when a scaled-up line can handle the least. In older homes, drain lines run decades ago on a lazy slope compound the problem - there is not enough fall to flush the sludge through, so it collects until it blocks.
Signs it's this, not something else
- The water is clear and shows up near the indoor air handler or drain line, not a refrigerant issue
- The drain pan is full or overflowing while the line stays dry, pointing to a blockage downstream
- Water appears only when the system runs and stops when it is off, which is consistent with condensate rather than a plumbing leak
- Ice on the coil or lines alongside the water suggests a frozen coil thawing instead of a simple clog
- A steady drip from a secondary or overflow line outside, which is a deliberate warning that the primary drain is blocked
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Frequently asked questions
Is this a refrigerant leak or a water leak?
They are completely different problems that get confused. Refrigerant is a gas under pressure and does not puddle - a refrigerant leak shows up as weak cooling, ice, or a hissing sound, not water on the floor. Clear water pooling near the indoor unit is condensate that cannot drain. If you are seeing actual liquid water, it is a drainage issue, not refrigerant.
Can I keep running it, or do I need to shut it off?
Turn it off at the thermostat until the drain is cleared. A running system keeps making water, so leaving it on just feeds more moisture into your floors, walls, and the air handler's electronics. Shut it down, slide a towel or pan under the drip, and you will limit the damage while you wait.
Is a clogged drain something I can clear myself, or does it need a tech?
You can try the easy version - find the outdoor end of the drain line and pull the clog with a wet/dry vacuum. If flow returns and the pan drains, great. But if the pan refills, the blockage is farther in, and in this area's hard water it is often mineral scale that needs the line properly flushed. That is when it is worth a professional.
Why is it leaking now, when it has been fine for years?
Drain clogs build gradually - algae and mineral scale accumulate over seasons until the passage finally closes, and it tends to happen mid-summer when the system is producing the most condensate. It leaks suddenly because that is the moment the narrowed line can no longer keep up with the water load, even though the buildup was months in the making.
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