Water – reuse cold water copper pipes for hot water

The safest way to bend a copper pipe is to use a pipe bending spring. They come in sizes to fit the diameter your pipe so you'll need two - one for each type of pipe. The spring stops the pipe kinking by supplying support to the inner part of the bend.

Simply slide the spring up the pipe, bend it and then work the spring out.

If you have the opportunity to replace your galvanized pipes, do so. It's an inconvenient project, involving opening up a lot of walls, but as you can tell from the comments, galvanized pipe is problematic at best over the long term.

It will frequently develop (as is the case in my own home and in my rentals) pin hole leaks. The only good news with galvanized on that front is - the gumming will often re-seal those pinhole leaks, but not all the time, as my basement ceiling could have attested, before I gutted the whole thing.