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Water where there should not be water.
Where the water from an air conditioner is supposed to go, the five places it ends up instead, and how we trace a leak back to its cause — in houses and in commercial buildings north of Houston.
Where the water is supposed to go.
Every air conditioner in this climate removes water from the air all day. That water follows a path, and every leak is a break somewhere along it.
- 1 · The coil
- Moisture condensesWarm, humid air crosses the cold indoor coil and water forms on the fins, running down into the pan beneath.
- 2 · The primary pan
- Water is caughtA pan built into the air handler collects it and feeds the drain connection.
- 3 · The trap
- Air is kept outA properly installed trap stops the fan pulling air back up the drain line — without it, water can be held in the pan instead of draining.
- 4 · The drain line
- Water leavesA sloped line carries it to a drain inside or to the outside. In a humid climate, algae and sludge grow in it.
- 5 · The safety layer
- A second pan and a switchWhere the unit sits above a finished space, a secondary pan underneath catches overflow, with its own drain and a float switch that shuts the system off if water rises.
Five places the water ends up instead.
1. The drain line blocks
The most common cause by far. Algae and sludge build up in the line until water backs up into the pan and over the edge. With a working float switch, the system stops itself. Without one, the ceiling finds out first.
2. The pan rusts through
Older metal pans corrode in constant contact with water. The first sign is often a stain directly under the air handler even though the drain line is clear.
3. The trap is wrong or missing
A missing, dried-out or badly placed trap lets the fan hold water up in the pan. It overflows while the system is running and seems fine when it is off — which makes it confusing to diagnose.
4. Ducts and boots sweat
A supply duct carries cold air through an attic full of hot, humid air. If its insulation is torn, compressed or missing, water condenses on the outside and drips — often at the boot behind a ceiling vent.
5. Rooftop condensate runs astray
On commercial roofs, condensate lines from packaged units need traps too, and they often lack them or clog. The water pools on the roof, around the curb, or finds its way inside.
The two parts that turn a leak into a shutdown.
Neither prevents a blockage. Both prevent a blockage from becoming a ceiling repair.
- The secondary pan catches what the primary pan cannot, and drains it to a place you will see — often a pipe dripping high on an outside wall. If you ever see water coming from there, the primary drain has failed.
- The float switch cuts power to the cooling when water rises. If your system has stopped for no obvious reason in summer, check whether the pan has water in it before assuming something expensive has failed.
- We test both on every service visit, by putting water where it would go in a failure and watching what happens.
How we find the source.
A stain tells you where the water arrived, not where it came from. Water can run along a duct or a joist for a long way before it drips.
Follow the path
Coil, primary pan, trap, line, secondary pan, switch — each checked in order.
Look at the cold surfaces
Ducts, boots, plenums and refrigerant lines inspected for sweating and missing insulation.
Test with water
Water poured through the drain path to see where it goes and whether the switch trips.
Show you
Photographs of the cause, and a written price to fix it.
On commercial buildings.
A building with several rooftop units has several condensate systems on its roof, and each one can fail on its own. The signs inside are ceiling tiles that stain and get replaced, only to stain again; diffusers that drip on humid afternoons; and carpet that is damp near a return.
We check every unit's trap and line, clear them, correct traps that are missing or wrongly sized, and make sure the water ends up at a roof drain rather than ponding around a curb. Above ceilings, we look at duct and diffuser insulation the same way we would in a house attic.
Each unit gets its own line in a written note, so a property manager can see which units were clear, which were cleared and which need work.
What this page doesn't cover.
Primeway fixes the HVAC side of a water problem: the drainage, the pans, the switches, the insulation on cold surfaces, and the equipment. We do not repair drywall or ceilings, we are not a roofing contractor, and we are not a mould-remediation company. If we find damage that needs one of those trades, we tell you and show you what we saw.
We also do not make health claims about moisture or mould, and we do not advise on insurance. Those questions belong with the right professionals.
Straight answers.
Can I clear the drain line myself?
Some homeowners do, and on many systems there is an access point for it. If you are comfortable doing it safely with the power off, it can buy time. It does not fix a missing trap, a rusted pan or a sweating duct — and if the line blocks again quickly, something else is going on.
How often should the drain be checked?
At every seasonal service at the least. In this climate, drain lines are one of the most common things we find partly blocked on a routine visit.
Is a sweating duct dangerous?
It is a water problem rather than a safety one: the damage comes from the water it drips onto insulation, drywall and ceilings over time. It is worth fixing before it becomes a ceiling repair.
Is this the same as my house feeling humid?
Related but different. This page is about liquid water in the wrong place. A house that feels clammy even when it is cool is a different question — about how the system is sized and set up — and we look at that too if it is part of what you are seeing.
Seeing water? Switch off, then call.
We will tell you on the phone what is likely and how soon we can be there.