Water Stain on the Ceiling: Is It the Roof, the Air Conditioner or a Pipe?
A water stain on the ceiling usually comes from one of three places: the roof, the air conditioner, or a pipe. You can often tell which by noticing when the stain appears, what is above it, and whether it follows rain.
Do these checks from inside the house. You do not need to climb on the roof, and you should not.
Start with the timing
The first question is when the stain showed up or grew.
If it grew during or right after rain, the roof is the likely source. A recent downpour is a common clue.
If it appeared on a hot, dry day while the air conditioner was running, think air conditioning. Condensation from cooling equipment and ducts happens in hot weather.
If it grows with no link to rain or to the air conditioner, a pipe is possible, because pipes can leak at any time.
Look at what is above the stain
Location tells you a lot.
Roof: a stain under a roof vent pipe, a skylight, a chimney or an outside wall is a clue. Stains near the edge of the room can also come from a gutter or roofline leak.
Air conditioner: if the air handler or a duct is above the stain, look there first. A stain that runs in a straight line can follow the path of a duct.
Plumbing: a stain under a bathroom, kitchen or laundry room, or one that sits below a fixture or a water pipe, points to plumbing. A stain that spreads in a large circle may also come from a pipe.
Check the air conditioner
If the air handler is in the attic or a closet, look at its drain pan and drain line outlet. Standing water in the pan, or a drain line that is dripping or backed up, means the air conditioner is making the water.
An air conditioner or plumbing problem is not a roofing job. If you find water in the pan or a wet pipe, call an air conditioning technician or a plumber.
Signs that point to the roof
A stain that grows after rain and does not grow in dry weather. A stain near a vent pipe, chimney or skylight. A stain that shows up only in storms with wind.
Remember that the stain is rarely right under the entry point. Water on a roof travels along the underlayment, decking and framing before it drips. We explain this in how we find a roof leak.
What not to do
Do not climb on the roof to look for the leak. Desert roofs are hot, steep and slick with grit.
Do not paint over the stain yet. Fresh paint hides the evidence, and if the water source is still active, the stain will come back through it.
Do not poke at a ceiling that is sagging or bulging with water. Keep clear of it and call for help.
If you still cannot tell
Take photos of the stain now, and again after the next rain. Write down the date and what the weather and air conditioner were doing. Those notes help whoever comes to look.
If the stain follows rain or sits near a roof feature, send the photos to us. Our roof leak detection page explains how we trace a leak from the stain back to the roof. If the roof is the cause, our roof repair page covers what we fix.
Why it matters to check quickly
Whatever the source, trapped moisture can cause mold and damage to the framing. A small stain is the right time to find the cause. For the most common roof causes, see the most common roof-leak sources in Las Vegas homes.
Frequently Asked Questions
How can I tell a roof leak from an air conditioner leak?
Timing and location. A roof leak follows rain. An air conditioner leak follows cooling weather and sits near the air handler or ducts.
Can condensation cause a ceiling stain?
Yes. Condensation on cooling equipment and ducts can drip onto a ceiling in hot weather.
Should I paint over the stain?
Not until the source is found and fixed. The stain will come back if the water is still coming in.
Will you come out if it turns out not to be the roof?
If the checks point away from the roof, an air conditioning technician or a plumber is the right call. If you are not sure, send photos and we will look at them.
Who do I call?
Call or text photos to (725) 502-3114.