Soldering Lead-Free Ball Valves requires a different approach to standard ball valves. Lead-free ball valves are required on all potable water lines. Meaning water going to all sinks, toilets, water heaters, most indoor plumbing. Lead-free ball valves shouldn't be heated 420-450 degrees Fahrenheit. First, clean the ball valve and copper, and apply flux. Next push pipe into ball valve fittings. After that start by applying heat to the pipe, next heat up the fitting, melt solder filling the joint. Finally, clean the fitting. Also, use a solder with a lower melting point. I prefer using a 95/5 solder.