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:
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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