PEX Pipe Installation

This page covers partial PEX work: new runs for a remodel, an addition or a relocated fixture group; a PEX repipe of one zone or floor; section replacement in PEX; and transitions to copper, CPVC or galvanized steel. The full project, staging and water-off windows included, is Whole-House Repiping. Which run has failed and where sound pipe starts is Pipe Replacement, the run-by-run job in any material; the galvanized verdict is Galvanized Pipe Replacement. A leak in existing PEX is Pipe Repair, freeze protection is Pipe Insulation, buried tubing to the meter is the water lines section, and PEX versus copper has its own guide.

What brings PEX into a house:

• A remodel that moves fixtures. A kitchen crossing the room, a bathroom gaining a sink: new runs laid while the walls are open.
• An addition or finished space. A new zone fed from the old one; the tie-in sets the transition fitting, the framing sets the support work.
• One zone in legacy material. A galvanized gallery or a polybutylene branch, scoped on Pipe Replacement or Galvanized Pipe Replacement and executed here in PEX.
• A freeze-path reroute. A run that froze moves into conditioned space. The 2021 International Plumbing Code, where adopted, bars water pipe from attics, crawl spaces, outside walls and other freezing locations unless protected by insulation or heat or both.

How the job is planned:

• Confirm the tubing is permitted. Under the 2021 International Plumbing Code, where adopted, water distribution tubing conforms to NSF 61 and a standard in Table 605.4, which lists PEX under ASTM F876 and CSA B137.5; hot water pipe is rated at least 100 psi at 180 F.
• One listed system, start to finish. The 2021 IPC ties fittings to the standards factory marked on the tubing; its fitting table lists ASTM F1807, F1960, F2080, F2098 and F2159, plus push-fit to ASSE 1061. Uponor's ProPEX is ASTM F1960 cold expansion.
• Layout for the zone. PPI's design guide names three layouts: trunk and branch; home-run, each fixture on an unbroken line from a central manifold; remote manifold, a trunk to a small manifold near a fixture group. Valved manifolds stay accessible.
• The water heater end. Uponor allows direct connection to electric heaters where local code allows; the 2021 Uniform Plumbing Code, as adopted in Hawaii, keeps PEX out of the first 18 inches of piping connected to a water heater.

What the scope states:

• Support and bends. The 2021 IPC hanger table, where adopted, supports PEX every 32 inches horizontally at 1 inch and smaller, every 4 feet at 1 1/4 inch and larger, and every 10 feet vertically, mid-story guide at 2 inches and smaller. Bend radius follows the manual: six times the outside diameter for Uponor, five with bend supports for Viega.
• Framing and light. Tubing passing a stud, joist or rafter less than 1 1/4 inches from the edge, concealed, gets No. 16 gage steel shield plates under the 2021 IPC where adopted. Tubing left exposed to sunlight after installation gets a UV-blocking sleeve or approved insulation per PPI's guide.
• Transitions to what stays. Under the 2021 IPC, where adopted, plastic meets other material through approved adapters or transition fittings; copper meets galvanized steel through a copper-alloy or dielectric fitting or an ASSE 1079 dielectric union. PPI has copper adapters soldered and cooled before PEX attaches, since heat above 180 F may damage the tubing.
• The pressure test. The 2021 IPC, where adopted, tests the completed section at not less than working pressure with potable water for at least 15 minutes; its 50 psi air test is for non-plastic piping only. Uponor's residential steps pressurize to 25 psi above working pressure or 100 psi, then test per local code.

• Pipes & Repiping

• Repair, Replace the Run, or Repipe? The Escalation Ladder
• PEX vs Copper: Which Pipe Wins Where
• Whole-House Repipe Cost: What Sets the Number