There are three main ways to configure a PEX plumbing system. These configurations are the trunk-and-branch system, the home-run system, and the remote manifold system. To choose the proper system for the home, consider each configuration's characteristics, and determine which characteristics are the most important. For instance, if the plumbing system needs to respond quickly to hot water demands, have few connections, and sustain water pressure to multiple fixtures, then the best choice is probably the home-run system, which excels in each of these areas. It's also important to consider the type of home, such as colonial or ranch, when making your descision. The type of home can affect how the plumbing system performs and how much it costs to install.
Trunk-and-branch system
A PEX trunk-and-branch system is very similar to a traditional copper pipe system. It uses trunk lines to supply smaller branch lines, which run to fixtures. However, a PEX trunk-and-branch system reduces or eliminates the need for coupling fittings. In addition, the flexible nature of PEX allows for sweeping turns, instead of elbow fittings. Although PEX and copper trunk-and-branch systems have many similarities, PEX has fewer fittings and fewer potential leaks.
Home-run system
A PEX home-run system uses hot and cold water manifolds to supply water throughout the home. The main water line and water heater line feed the manifolds; smaller lines run from the manifolds to the individual fixtures. The manifolds are installed in a central location in the home, typically in a basement, service closet, or other accessible place. The hot water manifold is installed near the water heater, but not closer than 18”, to improve the response time of hot water. The cold water manifold is typically installed beside the hot water manifold. With a home-run system, it’s possible to eliminate all fittings between the manifold and a fixture, increasing flow capacity and drastically reducing the chance for leaky fittings.
Remote manifold system
A PEX remote manifold system combines elements from both the trunk-and-branch system and the home-run system. In this system, remote manifolds are installed in convenient locations near multiple fixtures. Hot and cold trunk lines run to the remote manifolds, where individual branch lines then run to each fixture. Remote manifold systems use more fittings than home-run systems but fewer fittings than trunk-and-branch systems. They need far less pipe than home-run systems, which use the most piping of the three configurations. For other plumbing-related information and more in-depth installation Best Practices®, check out BuildIQ University’s online training course, Mechanicals: Plumbing.
