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Green Basics

Efficient Plumbing Supply Layouts

Home-run Layouts from a Manifold Have a Few Advantages


Sound planning saves energy

Heat losses increase with the diameter of the line, the distance the water must travel, and inversely with the speed at which the water moves. A large volume of slow-moving water sheds more heat as it travels to its destination than a smaller amount of water moving quickly.

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:

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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.

  3. user-7619767 | | #3

    Hello. We are building a new construction, high end house and want water distributed to all areas of the house to have the following: Consistent hot water. So when the washing machine is receiving hot water, somebody showering doesn't feel any effect, either from pressure or temperature. We also are planning to use tankless water heaters and a recirculating system. What is the best system design to accomplish these goals?

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