Step 5 · Prepare Pipe and New Sillcock for Soldering
Proper preparation is key to a leak-free solder joint. First, clean the end of the copper supply pipe inside the house. Use a pipe cleaning brush or emery cloth to sand the outside of the pipe end until it is shiny and free of oxidation or old solder. Do the same for the inside of the new sillcock's sweat connection. After cleaning, use a small brush to apply a thin, even layer of flux paste to both the outside of the pipe and the inside of the sillcock fitting. Before inserting the new sillcock, open its handle about halfway. This prevents pressure from building up during soldering which could damage the internal seals.