Manifold

A manifold is a central pipe fitting with multiple outlet ports that distributes water from a single supply line to multiple individual branch lines, each with its own shutoff valve. In plumbing, manifolds are the cornerstone of home-run PEX systems, where each fixture gets its own dedicated supply line running directly from the manifold rather than sharing trunk lines with other fixtures.

How a home-run manifold system works

The hot and cold supply lines from the water heater connect to the hot and cold manifolds, typically mounted in a utility room, mechanical closet, or under-stair space. Each outlet on the manifold connects to a single, dedicated ½" PEX tube that runs continuously — through walls, under floors, or through the attic — to a single fixture (toilet, sink, shower, dishwasher, etc.). Each outlet has its own shutoff valve at the manifold, so any fixture can be isolated and repaired without shutting off water to the rest of the house.

Advantages over trunk-and-branch systems

• Individual isolation: shutting off a toilet doesn't affect the shower or kitchen — ideal for repairs
• No shared pressure drops: each fixture has a dedicated line, so pressure doesn't drop when multiple fixtures run simultaneously
• Fewer joints: each run is a single continuous piece of PEX from manifold to fixture, with joints only at the two endpoints — dramatically reducing leak risk
• Faster hot water: smaller-diameter dedicated lines hold less cold water volume than shared trunk lines, so hot water arrives faster

Manifold vs. trunk-and-branch

Traditional trunk-and-branch systems use large trunk lines (¾") that run through the building with ½" branches tapping off to each fixture. This uses less total pipe length but creates multiple joints throughout the structure and more potential for simultaneous-use pressure drops. Modern new construction increasingly favors manifold systems for their serviceability and performance advantages.