Remove old solder?

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I had to disassemble a sweat joint on 1/2" cu. tubing.  I'll be putting a new elbow back on the existing tubing.  Question - Can I leave the old solder on the  tubing and put the flux over it?If it makes a difference, the tubing is vertical so the joint would be overhead.Thanks
Reply:Clean is mean...clean it as best you can, put on new solder.John -  fabricator extraordinaire, car nut!-  bleeding Miller blue! http://www.weldfabzone.com
Reply:keep the solder hot and wipe off as much as you can with a rag. Make sure to bush and sand real good and use lots of paste when reassembling.Miller DVI2Lincoln Precision Tig 225Thermodynamics Cutmaster 38Everything else needed.
Reply:I'm not a plumber, but my plumbing job did pass inspection   Personally I would cut the solder end off a couple of inches back and put a sleeve and little extension on there before I would try to re-solder a pipe end.  I would be worried about removing too much material when cleaning the solder down to bare metal, then not getting a good fit and bad flow when soldering the new joint on.
Reply:Just wipe it off hot and make sure its clean.  The solder that is already on the pipe will actually help if you are using he same type.  Do NOT drown the joint with flux, a thin brushing will do ya.  clean all the flux (acid) off the joint while the pipe is hot with a moist rag.  If toy don't wipe the joint when finished and there is enough flux left over it will eat up the pipe...
Reply:Real fine copper wool.  They sell the stuff at electrical stores.  Stick it on when when the solder is melted and it wicks it up.
Reply:After wiping off the hot joint, a little emery cloth will smooth things up, then a light coat of flux and solder as usual, yeah?
Reply:Heat it, wipe it quickly with a slightly damp cloth, assemble it, touch a SMALL amount of flux to the joint area after reheating, sweat the solder in.After two joints (no...not those kind!!), you'll be an expert.