: What is the best way to resolder pipe that has been solder'd, tested, and leaks?? When I do it the second time, the solder will not adhere to the fitting...
Drain the pipe completely. Remove the leaky fitting completely. sandpaper the copper pipe ends and the inside of the fitting. Don't get any fingerprints on the pipe ends or inside the fittings. USE FLUX.Put the fitting and pipe together. MAKE SURE IT IS DRAINED COMPLETELY. Heat the fitting evenly and apply solder till the joint is filled completely and squeezes out a drop that isn't solidifying, but is liquid. You are trying to solder a line that has water in it. The heat is boiling the water which generates a greater steam pressure inside the line than the outside air pressure so the steam squeezes past your liquid solder and causes a pinhole leak or two, while the solder is solidifying.