How to Repipe a House With PEX: Planning, Running Lines, Cutover

Repiping a 2-bath house in PEX yourself: $1,465–$1,980 in pipe, fittings, tools and permit, 35–60 hours — only with a homeowner permit.

Before you start

Read the cost comparison first. This guide is for a PEX repipe in a house where a homeowner can pull the permit and the pipe runs are reachable from a crawl space, basement or attic. That job saves about $5,800 on a 2-bath house and is within reach of a careful DIYer with a few weekends.

It isn’t for a house on a slab, for pipes buried in finished tiled walls, for copper, or for anywhere the work is restricted to licensed plumbers. Those aren’t harder versions of the same job; they’re different jobs, and the hire-a-pro page covers them.

What you need

For a 1,500 sq ft 2-bath house: about 400 ft of PEX (mostly 1/2 in, with 3/4 in for the trunk), the matching fittings, rings, drop-ear elbows and stub-outs, angle stops and braided supply lines for every fixture, a new full-port main shutoff, hose bibbs, water heater connectors, nail plates and hangers, pipe insulation for unconditioned spaces, and drywall patching supplies. Tools: a crimp or clamp tool with go/no-go gauge, a PEX cutter, an oscillating multi-tool, a drill with spade bits, drywall knives, a headlamp and knee pads. The priced list is on the cost page.

The two things that decide how it turns out

The permit and the test. They aren’t bureaucracy; they’re the only external check on work that’s about to be sealed inside walls. The pressure test at rough-in finds the one crimp in sixty that’s wrong. Do it before the inspector does, and patch nothing until it passes.

Alongside, then cut over. Building the whole new system next to the old one is more pipe and more planning, but it means your family has water every day but one, and it lets you test everything before it carries a drop. Trying to replace one line at a time is how a two-week job becomes a two-month one.

Step by step

1. Get the permit and plan the layout

   Apply for the plumbing permit as a homeowner and confirm the inspection sequence and test pressure. Then map the house: every fixture, the water heater, hose bibbs, the main shutoff, and the path from each to a crawl space, basement or attic. Decide trunk-and-branch (3/4 in trunk, 1/2 in branches) or a manifold system. Count fittings, stub-outs and angle stops from the map and buy 20% extra tubing.

2. Open the walls

   Turn off the breaker for any circuit in the wall. Cut a clean rectangle between studs behind or below each fixture with the multi-tool, big enough to reach the old stub-out and mount the new one — 8×12 in is typical. Open the water heater and main shutoff areas. Save the cutouts; some can go back as patches. Photograph what's in each bay before you run anything.

3. Install the new main shutoff

   Tee a new full-port ball valve into the main line just after the existing shutoff (or the meter side, per local code), with a short stub for the new system, closed. Add a pressure-reducing valve if static pressure is over 80 psi. This lets the new system be built and tested while the old one stays live.

4. Run the trunk lines

   Route 3/4 in PEX from the new shutoff to the water heater and along the main path toward each bathroom group, through the crawl space, basement or attic. Drill holes in framing at least 1.25 in from the edge and use nail plates where the pipe passes within 1.25 in of a face. Support every 32 in horizontally and at each floor vertically, with hangers that don't pinch. Keep hot and cold at least 6 in apart and insulate any line in an unconditioned attic or exterior wall.

5. Branch to each fixture and set stub-outs

   Run 1/2 in from the trunk to each opening. Terminate with a drop-ear elbow screwed to blocking between the studs, positioned so the stub-out lands where the old one was, and fit a stub-out or a PEX-to-threaded adapter. Cap every one. Bend PEX gently — no tighter than the manufacturer's radius, about 8 times the diameter for 1/2 in — and use a bend support where it turns 90° out of a wall.

6. Crimp every joint and gauge it

   Cut square with the PEX cutter, slide the ring on, push the fitting fully home, position the ring 1/8–1/4 in from the tubing end, and crimp squarely with the tool held perpendicular. Check every crimp with the go/no-go gauge — it must fit the 'go' slot and not the 'no-go'. Re-crimp or cut out anything that fails. Mark each checked joint with a marker so you don't lose track.

7. Pressure test and get inspected

   With every stub-out capped, pump the system to the test pressure through a gauge on a hose bibb or the water heater connection and hold for the required time. A steady needle passes; any drop means a joint to find. Then call for the rough-in inspection with the walls still open. Don't patch a thing until it's signed off.

8. Cut over in one day

   Close the old shutoff and drain the old system from the lowest hose bibb. At each fixture, cut the old stub-out back, uncap the new one, fit the angle stops and braided supply lines, and connect the fixture. Connect the water heater (new flex connectors, expansion tank if required) and hose bibbs. Open the new shutoff slowly, bleed air from every faucet, and check every connection for drips over the next hour and again the next morning.

9. Patch, paint and close out

   Screw backing strips into the openings, fit the drywall patches, tape and mud in three coats, sand, match the texture and paint. Reinstall any cabinet backs or tile. Call for the final inspection, keep the permit and the passed test with the house documents, and tell your insurer the polybutylene or galvanized is gone.

What would this cost you? The house repiping calculator prices the DIY version with the tools you already own and a value on your time, next to a pro quote.