How to Install PEX Water Supply Lines

Planning Your PEX Layout

PEX can be installed in two configurations: trunk-and-branch (similar to traditional copper plumbing, with a main line and branches to each fixture) or home-run (dedicated lines from a central manifold to each fixture). Home-run systems use more tubing but eliminate joints in walls and allow individual fixture shut-off at the manifold. For most DIY projects, trunk-and-branch is simpler. Use 3/4-inch PEX for main supply lines and 1/2-inch for branches to individual fixtures.

Connection Methods

PEX offers several connection methods. Crimp connections use copper crimp rings and a crimp tool — the ring is placed over the fitting, and the tool compresses it for a permanent seal. Clamp (cinch) connections use stainless steel clamp rings with a ratcheting tool. Push-fit (SharkBite-style) connections require no special tools — simply push the pipe into the fitting until it clicks. Expansion connections use a PEX expansion tool to enlarge the pipe end before sliding it over a fitting. For DIY projects, push-fit or clamp connections are the most beginner-friendly.

Installation Best Practices

When running PEX through framing, drill holes at least twice the pipe diameter and use nail plates where pipes are within 1.5 inches of the stud face. Support horizontal PEX runs with hangers every 32 inches to prevent sagging. Do not expose PEX to direct sunlight — UV radiation degrades the material within months. Allow for expansion and contraction by avoiding tight, rigid installations — PEX expands about 1 inch per 10 feet of pipe for every 10-degree temperature increase. Use brass fittings (not plastic) for connections that will be concealed in walls.

Connecting PEX to Existing Plumbing

Transition from existing copper or CPVC to PEX using appropriate transition fittings. Push-fit transition fittings (like SharkBite) work with copper, CPVC, and PEX without soldering or gluing. For threaded connections, use brass male or female adapters. When connecting to a water heater, maintain at least 18 inches of rigid copper or CPVC pipe before transitioning to PEX — most codes require this to protect the PEX from heat at the heater connection. Always follow local plumbing codes, as PEX regulations vary by jurisdiction.