2-Flat: Replacing Galvanized Pipe with Copper

[Eric Kahn Gale]

I've owned a two-flat in Albany Park for about a year now. We've replaced the roof (18.5K, it was never torn off in 100 years) and redid kitchens and bathrooms. 

We're planning to replace our galvanized pipe with copper this summer. We'll be replacing the main line rising up from the basement floor and all the pipe in 2 kitchens and 3 bathrooms. 

We received an estimate for $8K from one plumbing company and $6K from a little guy plumber that we've worked with a lot. 

Neither of these estimates include replacing the drywall and tile that will need to be ripped out to get in the walls. 

Does anybody else have experience swapping our galvanized for copper or pex? What did it cost? Were there any unexpected issues?