SAN ANTONIO GUIDE

Water over the ceiling, and an air conditioner that quit

A brown ring on the ceiling, a drip beside the attic hatch, or cooling that stopped while the thermostat still asks for it. In many San Antonio houses the air handler sits above that ceiling, and a long humid season sends a steady stream of condensate through a small drain. The water is usually that condensate. The stain means stop the system. It does not mean tape a safety switch down so the blower comes back.

By Mike Maziarz · Sources checked October 12, 2026 · How we write these guides

What the water actually is

Cooling pulls moisture out of humid air. That water forms on the indoor coil, falls into a pan, and is supposed to leave through a drain. Hours of runtime on a San Antonio afternoon make a real stream, not a few drops. When the path clogs, the pan under an attic air handler fills. A float switch is often the last device that opens the control circuit and stops the equipment before the water finds the drywall.

That pattern is not the same as a refrigerant leak, and it is not the same as a water heater that has let go in a closet. Condensate is ordinary water the coil wrung out of the air. A refrigerant problem can still be involved if the coil froze and then thawed into the pan all at once. Ice and a sudden flood belong in the same note. A wet ceiling under the air handler is a cooling-side problem to sort. A wet spot at the water heater, with the air conditioner still draining normally, is a different trade.

The drain, the trap, and the film

The primary drain is usually a PVC line from the air handler toward a bath, a utility sink, or a termination you can sometimes see outside. A trap in that line holds a water seal. Over a long cooling season the trap grows a film of algae and dust. The stream slows, then stops, then the pan rises. A clear stream at a sink you have watched before is useful evidence that the line was open. No stream on a hot afternoon, while the system has been calling for cooling, is the opposite evidence.

A bottle of vinegar poured into a fitting you understand can clear a short, reachable trap. It can also push water into the wrong pan if you guessed the fitting. If the line disappears into the attic and you cannot see where it goes, leave the flush alone. Do not open the air handler cabinet to find a better hole. Do not bypass the float switch so you can watch whether the flush worked. The switch is what kept the ceiling dry up to now. A technician who clears the trap and then tests the switch has done the job. A homeowner who defeats the switch to finish the afternoon has started a water-damage job.

The secondary pan and the float switch

Many attic installations set the air handler in a second pan, or give the primary pan an overflow outlet, because the primary drain will clog eventually. That second pan is not a storage tank. It is a backup. Water sitting in it means the first path already failed. Rust in that pan, a water line on the metal, or a drip from an overflow outlet outside is a record of an earlier overflow, even if the ceiling looks fine today.

The float switch sits in that water path and opens when the level rises. The thermostat can still display a call for cooling. The outdoor unit stays quiet or the blower stops, and the house warms. People then bridge the switch with a jumper or a piece of tape. Do not do that, for an hour or for the night. The same advice is the short version on the page about rooms that stay warm while the condenser runs. This page is the water version: if the pan is the reason cooling stopped, the repair is the drain and a working switch, not a defeated switch and a wet ceiling.

When the water has already reached the drywall

A stain, a bulge, or an active drip means water has already left the pan. Turn cooling off at the thermostat so the coil stops making more water. Stay out from under a bulge. A wet ceiling can fail without much warning, and the insulation above it can hold a surprising amount of water. Do not poke the stain to see what comes out. Do not run the fan in the hope that moving air will dry a soaked attic before anyone looks.

Write down which room, which floor, and whether the stain is under a bathroom, under the hatch, or under a hallway that has no plumbing of its own. A stain with no pipe above it, in a house whose air handler is in the attic, points back at the pan. A stain that grows only when someone showers points somewhere else. Photos from the floor, taken before anyone walks the attic, keep the story straight. If someone already climbed up, say whether the secondary pan had standing water, and say whether the switch was still connected.

Checks that stay on the floor

You can do a few things without opening a cabinet. Set the thermostat so the system is not calling for cooling if water is reaching the ceiling. If the filter lives in a hallway return you can reach, look at it. A packed filter starves the coil, the coil can ice, and the thaw floods a pan that was only barely keeping up. Replacing that filter is a homeowner check. A filter door on the air handler, up a hot attic ladder, is not a casual errand on a summer afternoon. If you are not steady on the ladder, or the attic is too hot to think, leave the hatch shut.

Look outside, or at a sink the installer used as the drain end, for a stream while the system has been running and the ceiling is still dry. Note whether an overflow outlet is dripping. That drip is a warning that the primary line is not doing the work, not a sign that everything is fine. Do not stand in water and reset breakers to force the unit on. If the outdoor unit is also humming with a fan that will not turn, that is a separate electrical fault in a fan that will not spin, and it is not fixed by clearing a drain. Shut cooling off and treat them as two notes, not one experiment.

When the pan is a technician job

Call when the ceiling is wet, when the secondary pan has water in it, when cooling stopped and you suspect the switch, or when the clog has come back after a cleaning. Call when ice and water showed up together, because a thaw can imitate a drain failure that actually started as weak airflow or a refrigerant problem. The visit should say whether the trap was cleared, whether the pan slopes, whether the switch was tested, and whether the coil was wet from a clog or wet from melting ice. Those are different repairs.

The person who opens the attic equipment should be a licensed air conditioning contractor. The Texas Department of Licensing and Regulation licenses that trade, and the lookup is the check before anyone climbs the hatch. A license is not a promise about this drain, and this site does not send the technician. If the house is already dangerously hot because cooling is off, older adults, infants, and anyone who feels ill should not wait under that ceiling. Move them, and use the same-day steps in no cooling on a dangerous afternoon. A clogged drain is a repair. A hot house with vulnerable people in it is a reason to leave.