I am not a plumber, but I soldered a T-tting into a ½" copper pipe, using a propane torch. I used flux (which was 10 years old, does it expire?) but unfortunately, it has a slight leak because apparently not enough solder got into one of the joints. Then I tried to touch up by adding more solder, but it ended up just getting a glob of solder on top without fixing the leak. Is there a way for me to get the solder in there to stop the leak, without replacing the T-fitting?

Sometimes it works. Sometimes it doesn't and you have to replace the fitting.

Did you prep it properly by sanding or using the tool for the connected pieces?

If your uncomfortable soldering or if this is now a repair, you can pre-tin both pieces and wipe with a damp cloth and pre fit.

In general, your heating one side of the fitting and applying solder to the other side.

Sometimes the issue is water.

Also make sure there is an opening in the system while soldering.

At this point, you may be able to reuse the fitting.

KeepItSimpleStupid have stated very well follow his instruction for more info please open the link below and will show you step by step how to solder, good luck.

John

Working with Copper Pipe | DoItYourself.com (http://www.doityourself.com/stry/h2handlecopper)

I am not a plumber, but I soldered a T-tting into a ½" copper pipe, using a propane torch. I used flux (which was 10 years old, does it expire?) but unfortunately, it has a slight leak because apparently not enough solder got into one of the joints. Then I tried to touch up by adding more solder, but it ended up just getting a glob of solder on top without fixing the leak. Is there a way for me to get the solder in there to stop the leak, without replacing the T-fitting?
Shut the water off and blow the line clear with a compressor or air bottle. Leave the line open for steam to escape and commence to heat the tee and boil the moisture out. When the solder begins to run swab the joint with flux and run the tip of your solder around the joint while applying more heat. When the solder gets sucked in the joint you have a good solder joint. Good luck, Tom

As said above: NO WATER in the pipe is the key word. Then, make sure you heat the fitting up well. Sometimes you can touch it up w/o taking the joint apart - but as I learned long time ago - it is the fastest fix if you just take it apart, clean again, re-apply flux and resolder.

Milo,
the fastest fix if you just take it apart, clean again
That's what you and I would do. However for the asker this will give him 4 joints to clean,flux, and solder. My way would not have him cut the pipe and add a coupling.

While that might not be the easiest or fastest but it's for certain the simplest. Regards, Tom