I am replacing my outdoor spigot. Our home is over 100 years old and has mostly galvanized pipe, some sections that feed the water heater and sink are copper with dielectric unions at the junctions with the older pipe. I replaced the spigot's shutoff/waste drain valve in my basement with a brass type valve. I decided to also replace our outdoor spigot which attaches to this valve via a 9-ft length of galvanized pipe.

In doing so, I want to replace that 9' run with copper pipe. In looking at the IL code they mention using either a dielectric union or a "brass converter fitting". Doing some research, I found that "6" hardened brass nipple" is a suitable union. Is this what the IL code referring to? If so, is it best for me to attach this union before, or after, the shutoff/waste drain valve in the basement, i.e., does it matter which side of the brass valve I attach it to before attaching the copper pipe? I suspect it does not matter...but I want to make sure it agrees with code.