I have a tiny leak in a copper tee joint in the ceiling of a bathroom. It looks old, possibly from when the house was built (2003) and isn't actively leaking anymore-- maybe one drip a month? But it did some damage to the drywall below it and upon investigation I found the leak. My question is, can I clean the residue from the leaky area and seal it with one of those metal-epoxy products, and have it be water-tight? Or does it require re-sweating the tee to be really effective? Thanks in advance for any advice you can give.

You can try the epoxy method but a lot depends on house pressure. Don't use the epoxy tape. The only real way is to resweat.

How about a sharkbite? You get to cut a little extra copper off to fit into the larger tee.

Problem with a shark/gator bite is that the solder must be removed, typically by cutting. Then, the pipe is too short. I had to fix one today where they left <1/2" and it leaked.

Yes I agree with Ma064 try the epoxy method if it doesn't work, re-sweat or if you cut the pipe and have clean pipe for Sharkbite installation will work, good luck.

John