[HayZee518]

Galvanized steel pipe stinks for water supply lines. Chlorinated water, flouridated water plus the basic minerals in the water tend to build up deposits withing the pipe's walls - something like the plaque the medical folks say about arteries. Eventually the wall of the galvanized pipe will close up completely. Copper piping forms its own oxide coating inside and outside but it isn't affected by the minerals. If you mix galvanized and copper you need a dielectric union between the two. Galvanized steel is an electro-deposited coating of zinc. Without the dielectric union, right at the joint, you have a battery. And this "battery" generates a small voltage and starts to leach out minerals in the galvanized pipe which eats away at the joint. Eventually the pipe fails - water - water everywhere! For soldering copper joints use a lead free flux and a lead free solder.