
Green Basics

Efficient Plumbing Supply Layouts

Home-run Layouts from a Manifold Have a Few Advantages

Sound planning saves energy


For that reason, zoned trunk-and-branch systems (also known as structured plumbing) save water and energy compared to conventional trunk-and-branch systems or home-run (manifold) systems.

Heat loss in conventional systems. A 3/4-in. dia. supply line in a trunk-and-branch system holds a lot of water. When a hot-water tap is opened in a bathroom far from the water heater, all the water sitting in the 3/4-in. pipe must flow through the system before any hot water reaches the user.

In a home-run system, the tubing is usually only 3/8 in. or ½ in., so less water is wasted before hot water reaches the faucet.

Structured plumbing. To reduce the time it takes hot water to reach a remote faucet, save energy, and save water, green builders should install a type of plumbing system called “zoned trunk and branch” or “structured plumbing.” For more information on structured plumbing, see these two articles:

Home-run vs. trunk-and-branch system

In a trunk-and-branch system, the main supply lines, the “trunks,” carry water to the general area where it will be used. Smaller-diameter tubing, the “branch” lines, get water to showerheads, faucets and other points of use. In residential construction, trunks are often ¾-in. dia. and branch lines ½ in.

In a manifold system (also called a “home-run” system), the hot water and cold water supply lines feed a manifold that distributes hot and cold water to each fixture in the house. Each fixture gets a dedicated run of tubing from the manifold.

Manifolds are like main electric panels.…

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  1. Al Shawa | | #1

    What is the best type of PEX pipes to use ?
    Which is the best price?
    Do I need to insulate PEX pipes?

  2. User avater GBA Editor
    Martin Holladay | | #2

    Response to Al Shawa
    Al Shawa,
    Q. "What is the best type of PEX pipes to use?"

    A. These days, PEX tubing is a fairly generic product. Although several manufacturers vie for the market, I doubt if you will find major quality differences between the different products.

    Q. "Which is the best price?"

    A. That's a question that can only be answered locally.

    Q. "Do I need to insulate PEX pipes?"

    A. Yes.

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