Modernize plumbing and insulating for cold

[Makalu1]

I’ve got a 2001 E350RB50 van. Its under-seat plumbing is a mix of materials and takes the longest way to get from point A to point B possible, I suspect a result of some poor repair work. The water lines are also prone to freezing on long cold nights. I want to replace the lines and insulate them, hopefully sacrificing as little precious space as possible.

I’m sure I’m not the first to deal with this. Any links, suggestions or pics to help me with this project will be appreciated! Even some shots of how it’s done on new vehicles might help.

Thanks!
Scott Madsen, Salt Lake City, UT