I’ve added a note to the Fly Sparge HowTo Post. This was because I used galvanized steel on the sparge tank and I really shouldn’t. So stainless steel or copper will replace that when I get the chance (and money). Here’s the note:
A note on materials: I used the aluminum stock pot because I have it. Aluminum is not as terrible as people think and I have no problem using it for my sparge water. CPVC is good up to 200° and so it is fine for everything up to boiling, and sparge water doesn’t go hotter than 180°. Stainless steel and copper are both good for all brewing purposes, galvanized is not, it rusts (although it is used for water lines; I’m not sure how that works).