previous
  • The Passive House Build
    The Passive House Build
  • All about Roofing
    All about Roofing
  • 9 Concrete Countertops Ideas
    9 Concrete Countertops Ideas
  • 7 Small Bathroom Layouts
    7 Small Bathroom Layouts
  • Deck Design & Construction
    Deck Design & Construction
  • Master Carpenter Videos
    Master Carpenter Videos
  • Tips & Techniques for Painting
    Tips & Techniques for Painting
  • Shorten a Prehung Door
    Shorten a Prehung Door
  • Read FHB on Your iPad
    Read FHB on Your iPad
  • Remodeling in Action
    Remodeling in Action
  • Magazine Departments
    Magazine Departments
  • Video: Build a curved step
    Video: Build a curved step
  • The Hobbit House and More
    The Hobbit House and More
  • Buyer's Guide to Insulation
    Buyer's Guide to Insulation
  • 7 Trim Carpentry Secrets
    7 Trim Carpentry Secrets
  • Play the Inspector Game!
    Play the Inspector Game!
  • 7 Smart Kitchen Solutions
    7 Smart Kitchen Solutions
  • How to Install Housewrap Solo
    How to Install Housewrap Solo
  • Basement Remodeling Tips
    Basement Remodeling Tips
  • 12 Remodeling Secrets
    12 Remodeling Secrets
  • Energy-Smart Details
    Energy-Smart Details
  • Clever daily tip in your inbox
    Clever daily tip in your inbox
  • Electrical Articles & Videos
    Electrical Articles & Videos
next

Save water with a home run

Q:

I plan to use PEX tubing throughout the house I’m building. Someone told me that compared to a traditional trunk-and-branch system, a home-run system with manifolds will save water and energy.


As far as I can tell, the distance hot water has to travel from the tank to a faucet or appliance is virtually the same in both systems. How does a home-run system save water and energy?





A:

Georg Efird, owner of A2Z Plumbing Inc. ( www.eatsleepplumb.com ) in Asheville, N.C., replies: First, let me recap the difference between the two systems. A trunk-and-branch system consists of several branch lines (usually 1/2 in. dia.) that run off a main trunk line (usually 3/4 in. dia.). A home-run manifold system consists of uninterrupted lines that run directly from a manifold to each fixture in a house.



   

The main water-saving benefit of a home-run system is that there is less tepid water to purge in hot-water lines. If you’re not purging as much tepid water, you’re also improving the hot-water delivery time, which in turn saves energy.


How is it possible that there's less water to purge? The simple fact is, the smaller lines in a home-run system carry less water. As an example, consider that a 3/4-in.-dia. line carries nearly twice the volume of water as a 1/2-in.-dia. line of the same length. Although water is traveling the same distance in both systems, less water is actually traveling through a home-run line than through the trunk or branch lines.

No matter which system you use, fittings create friction, and friction negatively impacts water pressure. Because there are so few fittings in a home-run system, home-run lines can be smaller than branch lines—as small as 3/8 in. dia.—without negatively impacting water pressure.


From Fine Homebuilding 196, pp. 92 May 14, 2008