Tracking down the water leak (floor, shingles, furnace, window)

[Hawnted]

Hello. I bought a brand new house in Dec 2006. Last night it was raining and my wife and I noticed a ceiling leak in the master bedroom on the first floor about 6 inches from the exterior wall, coming out of the air conditioning vent in the ceiling. We were not running heat or air at the time. Directly above that is the office and there is NO water anywhere in the office, nor in the ceiling. There is a dryer vent that goes out of the side of the house right by where this leak is. We are trying to track down where it is coming from. Is it possible that wind was blowing the rain into the dryer vent and leaking ? If not, what else should we look out for? There is a bathroom upstairs, but it is on the other side of the house, and I doubt the plumbing would run that close to the brick when the first floor bathroom is on the other side of the master.

[NorthmeetsSouth]

This is only a guess... but I would remove the cover of the vent and see if you can determine if the water is running down the ductwork. If the furnace is in the attic that is unlikely, but if it is in a dormered attic area on the second floor then that could be the problem. It may also be coming in from where the dryer vent goes through the siding and is dripping down through the vent because it is the path of least resistance. Is that smaller spot in the photo closer to the outside wall than the vent? If so, it may be puddling on top of the sheetrock and it would help to drill a hole or drive a nail there and make a small hole for the water to drip through so it doesn't soak the sheetrock.

[Hawnted]

That smaller spot is actually further away from the exterior wall.

[Poltracker]

I would initially suspect the dryer vent but, that could be coming from a leak in the roof upstairs and running between a wall and dripping on the ductwork then following it along. Wait till it stops raining then get out the hose and check all possible locations throughly.

[Hawnted]

How do you use a hose to check it?

[Ms. 01 Snake]

If it was raining last night when the spot appeared, there is a good change it is the result of wind driven rain on the roof, if there is any sort of plumbing jack or vent in that general area.
If the leak has stopped, I would bet that the storm was the problem. If the leak continues after the rain has ended, it is probably a plumbing leak between the 1st and 2nd floors.
If you are able to get onto your roof, check a round and see if there are any shingles missing or if the leak is in an area of any roof openings (jacks,vents ect) if not, get a roofer out to take a look for you. You might need some quick maintenance to these areas.

[K'ledgeBldr]

For water to show up that fast it would have to be that dryer vent- or some other wall penetration in that immediate area.
Check the dryer vent housing outside. Make sure there is a flapper in the the housing. Check to see if it swings freely. Check to see if the housing has been caulked around the perimeter.
If all appears to be correct- use a hose on these area- spray around, over, and down on the vent and see if the moisture returns.
Another way to "see" inside the floor cavity- remove the register from the supply boot, then look for screws around the perimeter of the opening- removing these screws will allow you to move the boot out of the way and see into the floor cavity.
One other possibility- is there a window directly above this location? If so, check the caulking around the window- especially around and under the sill/sill extension. Also, check the floor directly in front of this window for dampness.

[Hawnted]

Thanks for the responses guys. There is no window above this location. I am thinking that the wind blew the rain sideways into the dryer vent was my first guess, but was not sure if that seemed feasible. I will spray water on the vent and check it tonight