drywallpipe
I was drilling in my drywall to install a drywall screw, all of a sudden high-pressure air starts coming out, after awhile it stopped.
When I looked inside I could see copper pipe with the hole I just drilled.. What did I hit? I'm thinking it has something to do with my A/C as there was no water, just high-pressure air.
How would I go about fixing something like this?
You likely hit the DWV (drain waste vent) stack. This is the drain plumbing for the bathroom and is commonly black ABS plastic.
This pipe is typically empty except when waste is moving though it. Depending on the size of hole, you may find small water spots that gradually get larger or notice a sewer gas odor in that room or nearby rooms.
It is not too hard to apply a patch material to the puncture to fix, but you'd need to cut a good size hole in the drywall to access it. The other option would be to enlarge the hole enough to get the tip of a caulking gun in to fill the hole and then patch the drywall.
It sounds like you may have metal studs. That would explain the difficulty drilling through, followed by the void beyond.
Best Answer
Unless you have a home workshop with an air compressor (and I'm quite sure you don't) you have punctured your air conditioner refrigerant line and drained the system.
The "air" was actually refrigerant. While not toxic it's certainly not healthy and your room now has several pounds of it floating around at floor level.
You will want to do the following, more-or-less immediately:
remove any pets or children to upper floors or (better) somewhere else.
open windows
ventilate the room / floor. Rent an industrial fan with a large duct, put the fan in the room and the duct leading outside. Any rental place will have one. Tell them what happened or you will probably get a carpet-drying fan. We need to remove air, not move it around.
In the near future, you will be cutting open that part of the wall. Call an air conditioner serviceman with the make and model of your unit and tell him you punctured the line and drained the system. He will fix the line and refill it with new refrigerant. Don't try fixing the pipe yourself - the joint has to be gastight with the proper parts or it will leak again. The parts & labour for fixing the pipe will be less than the sales tax on the refrigerant, and the guy just might do it for no extra charge (sympathy for the $1000+ you're paying for new gas).