AC dripping water inside? It's the condensate line (fix it for $4)
Water pooling around your indoor AC unit is almost always a clogged condensate drain line. Algae builds up in the pipe, the water backs up, and it goes wherever it wants. The fix is a shop vac on the outside drain stub and a cup of vinegar down the line. About an hour the first time, $4 in parts.
- Wet/dry shop vac to pull the clog from the outside stub
- A rag to seal the hose to the pipe
The AC has been running more or less nonstop since the second week of June, because this is Virginia and July does not negotiate. Tuesday evening Deb stepped in something wet in the hallway by the air handler closet, and the look she gave me had a work order in it.
Here is what is happening when you find water there. Your AC pulls humidity out of the air, and in a July like this one that is gallons of water a day. All of it is supposed to leave through a little PVC pipe called the condensate drain line. Algae grows in that pipe because it is dark and wet and nobody ever thinks about it. The pipe clogs, the drain pan fills, and the water finds the floor. That is the whole mystery.
The fix
- Kill the AC at the thermostat first. No sense making more water while you work.
- Find the drain line outside. It is a white PVC stub near the outdoor unit, usually dripping in happier times.
- Seal your shop vac hose against that stub. A rag wrapped around the joint does it. Run the vac for a solid minute. You want to hear the clog arrive, and you will know it when you hear it. What came out of mine looked like something Biscuit would roll in.
- Inside, find the vent opening on the drain line near the air handler and pour in a cup of white vinegar to kill what is left of the algae. Use the plain 5% grocery vinegar. Not the 30% concentrated cleaning vinegar they sell at the hardware store, that stuff is a different animal and you do not need it here.
- Turn the AC back on and watch the outside stub. Steady dripping means you are done.
The float switch nobody tells you about
If your drain pan is full but the line looks clear, or the AC shut itself off entirely, look for a little plastic box riding on the pan or the line. That is a float switch, and its whole job is to kill the system before the pan overflows into your ceiling. Mine tripped, and I spent 20 minutes diagnosing a dead AC before I even knew that part existed. The fifty cent word I said when I finally found it is in the jar. Empty the pan, clear the line, and it resets itself.
How much vinegar, how often
A cup down the line once a month during cooling season. Set a reminder on the first of the month. It is a 2 minute chore that prevents the exact Tuesday I just had, and the gallon jug lives next to my filter stash now like it pays rent.
What went wrong
The 20 minutes on the float switch, which is why a 30 minute budget turned into 55. Learn from me. Check the switch first, then the line.
One warning, and I mean it. If the line is clear, the switch is happy, and water still shows up, you may be looking at a cracked drain pan or a frozen coil, and that is a pay-the-man situation. A service call runs somewhere around $75 to $250. Ceiling drywall, which is what that water is auditioning for, costs a lot more. This one goes in the spreadsheet as a $4 win, and I will take every one of those I can get.
The Damage
| Item | Where | Cost |
|---|---|---|
| Great Value distilled white vinegar, 1 gal (5% acidity) | Walmart | $3.94 |
| Sales tax | $0.24 | |
| Total | $4.18 |
Deb's verdict. "The hallway is dry and you smell like a salad. Good job."