AC Leaking Water? What the Puddle Is Telling You
Water where water shouldn't be gets homeowners' attention fast — especially under an attic unit, one ceiling away from a repair bill. The good news: an AC "leaking water" is usually the cheapest problem on the AC repair menu. Here's how to read it.
Standing rule, every page: if you ever smell gas — rotten eggs — leave the house and call your gas company from outside. That outranks everything below.
Where the water comes from
Your AC dehumidifies as it cools. On a humid day, a central system pulls gallons of water out of your air. All of it lands in a drain pan under the indoor coil and runs out through a drain line. Every drop you're seeing is supposed to exist — it's just not making it out the drain.
Suspect #1: a clogged drain line
The drain line grows algae and gunk, clogs, and the pan overflows. This is the overwhelming favorite. Clues: it's humid season, the water is at the indoor unit, and it built up gradually.
What to do now: - Mop up and keep an eye on the pan. - If your system has a safety float switch, it may shut the AC off before the pan overflows — so a "dead AC plus water" is actually good news: the safety worked. - The fix is clearing the line. Some homeowners do this at the outside drain stub; otherwise it's a quick, inexpensive service visit. Nothing else on the truck fixes it.
Suspect #2: melting ice
If you also have weak airflow, or you saw frost on the copper lines, the "leak" may be a frozen coil thawing — the ice melts faster than the drain can swallow. Check the filter: a clogged filter is the usual cause of the freeze. (We have a full page on ice: Ice on the AC line.)
Suspect #3: a cracked or rusted drain pan
Older systems' pans rust through. Clue: steady dripping from the middle of the unit even when the drain line is clear, on a system 15+ years old. That's a replacement part and a pro visit.
When water means hurry
- Water spreading toward a ceiling below, or near electrical parts — shut the system off at the thermostat now. Cooling can wait; a ceiling can't.
- Water plus a system that keeps running anyway — turn it off yourself and treat the drain as a today problem, not a someday problem.
Sort it out before you call
Our free troubleshooter asks where the water is, what the filter looks like, and how the system's behaving — the same phone triage a good shop runs — and tells you whether this is a DIY drain clear, a cheap visit, or a real repair.
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