if its on an elbow vent the water out of the line take a piece of steel wool and clean up both ends of the leaking fitting.flux around both exsisting joints...wipe unrolled solder with steel wool and dip it into the flux.your ready to solder!!!!!with solder in hand and the torch lit

....flash the flame over the flux on the solder rolled out so it melts down the piece(that preps that new solder)take the torch and point it onto the elbow bend... just bearly hittting it...know watch the exsisting solder melt go 360 degees around each joint and pull the torch away...your done!

in the future always redo both joints that close together just to make it solid...the biggest thing with soft soldering you have to be clean on all items involved and the water has to be out of the line,if not you will be just heating water in the line and the solder will never take and spit steam out.