Pex

Pex is a plastic piping for potable water delivery. It is also used in radiant heating systems and has been around for about 40 years. It just last year became legal in California after a long battle with the plumbers union. It took all of an hour to run both a hot and cold water line through five walls, which was about 20feet. With the nature of the round walls, this would have been an enormous undertaking using copper. I ended up plumbing the entire house in about a day.
The picture below shows the whole house water filter and the pex manifold. The manifolds are the key to the pex delivery system.


This is a picture from the kitchen sink. It's also where the on demand hot water tank is located.
The tank is pretty amazing, though I haven't put it through a real test yest. It is rated to provide enough water to the entire house, and since it's electric, there's no need for venting.


A seperate manifold system for the bathroom.
Normally you would run a single hot and cold manifold to the entire house, but I found locating one set in the bath and one in the kitchen was a bit easier, especially with the extra materials I had on hand.