"Home-run plumbing systems are gaining popularity in new construction for lots of great reasons, but plumbing changes in an existing house are sometimes very challenging. However, it can be a significant improvement in performance in some cases if some small changes can be made.
... Home-run plumbing relates to the design of the piping network supplying hot and cold potable water to the various fixtures and end points around the house. ..."
For the rest of the article: Eric Helton: Building Science -- Home-Run Plumbing (HGTVPro.com)