Does anyone know how to fix a leak you can't find!

Maybe you could put a fluorescent dye into the water line, and then go around with a black light.
Other possibilities include summoning a plumber and duct-taping the living daylights out of everything.

duct tape – would that work?

Soapy water if it was an air leak, as for a water leak, is it from an AC unit?

No, duct tape will not last. You need to repair the roof.
If not, then you need a ‘drip diversion system’. That is nothing other than finding a place to connect a plastic trash bag and aim the bag into a plastic trash can. Duct tape will work if it is covered in plastic. example; wrap one end of the trash bag around the pipe, tape it, lead the bag towards a plastic trash can. Not attractive but cheap and easy.
A water hose to the roof, in differing places, can spot the problem area. Just water areas until the leak appears. Water low to high to prevent run off from being considered as a problem area. Also, look around the a/c unit to see if the hose from the condensation is running into the house. Or anything else on the roof that produces water.
Good luck

The section of roof over her room needs to be examined and the leak repaired. If the roof was put on fairly recently there is probably a warranty for the materials and workmanship. Is it a flat roof? Has anyone been up on the roof recently, walking around? This could cause the seams of the material or what’s underneath it, to pop open.

Follow the trail of water….?

Okay, sorry that was rude, leaks are a pain, I know.

It seems that you don’t know with certainty whether this is a pipe leak or a roof leak, so that’s the first thing to find out. If it only drips when it rains, then it’s a good bet that it’s a roof leak, of course (though it could still be a roof drain if you have a flat roof with a built-up parapet, which is common).

If it’s a roof leak, then there’s almost no telling where the leak originates. Those things are notorious for coming in at any odd crack in the covering, a piece of damaged or unseated or improperly lapped flashing, or a piece of tar that held some flashing in place coming loose… and then that little bit of water can wander the width of the roof as it flows along a ceiling joist or roof beam until it finds the ‘right’ place to drip.

If it’s a pipe leak then it should be easier to find, since all you have to do (easy to say “all you have to do”, but harder to effect) is trace the various pipes in the ceiling to find which joint is leaking. But that usually is easier to do.

Assuming a roof leak, I’d recommend that you buy a 5-gallon bucket of roofing tar and a water hose and go on the roof during a decent spell of great dry weather. Thoroughly wet various parts of the roof and do the best you can at keeping the water contained in the smallish areas that you want to test. Check every tarred seam, piece of flashing, roof penetration, vent and drain that you can. Start with the area right over the leak (you may be incredibly lucky to find it there, but don’t count on it) and work outward slowly. If you end up doing the whole roof in one morning, for example, then you’ll still not know where the leak originates if it’s a small one and it migrates after it comes through the roof.

If you can isolate the “general” source of the leak then tar the hell out of that area, with particular attention to any place that shows a seam in the existing covering, a penetration, flashing, etc. And if you do have roof drains, make sure that they are unblocked and free-flowing, because water backing up in a drain can find a pipe seam and leak through the pipe, and it can also be dangerous to the structure to have undrained water backing up in a heavy rain.

Good luck.

thanks guys!
I think we are going with tarpaulin on the roof to stop it from getting into the bedroom!
the roof is a brooklyn roof so that means that there are always people walking around on it!
Winter though – sooo cold!

Do you own the building, or do you rent?

rent!

Have you called the landlord or super about it?

I think you probably have to find the leak to fix it it’s common sense.