In this video, I am soldering the final sweat connection, for my sprinkler system. I have a vertical copper fitting that faces down. First I clean the copper pipe and fittings. Next I ream out the inside of the pipe to reduce turbulence. Flux is needed to make solder flow around pipe. Over applying flux will lead to a runny messy solder joint. Therefore I show how to correctly apply flus. Finally I hear the copper pipe and melt solder into fitting.