Fixture-unit trunk sizing, home-run manifold ports and branch PEX footage for a whole-house repipe.
Estimates are planning aids, not a professional quote. Double-check quantities and product coverage — and any local code or permit requirements — before you buy.
⚠ Shut off the main and fully drain the existing system — including the water heater — before cutting into any line, and cap or remove the old piping as you go so hot and cold can't get cross-connected mid-job.
⚠ Most jurisdictions require a permit and inspection for a whole-house repipe, and some restrict which PEX type or fittings are code-approved locally — check before you buy fittings.
| Plumbing & Heating | $691–$936 |
| Insulation | $110–$149 |
| Fasteners & Hardware | $72–$98 |
| Connectors & Brackets | $70–$95 |
| Total | $944–$1,277 |
Excludes tools, delivery, tax and permit fees. Labor not included — this is a DIY materials estimate.
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About this calculator
Enter your bathroom, kitchen and laundry count and the PEX Repipe Calculator sizes a home-run supply system the way a plumber actually specs one: trunk pipe diameter comes off total supply fixture units against your household water pressure, not off square footage, and every fixture gets its own dedicated hot and/or cold line back to a central manifold. That's what tells you whether you're buying 3/4" or 1-1/4" trunk, and how many ports each manifold needs.
It also converts fixture counts into home-run branch lines split by flow — 3/8" to toilets and lavs, 1/2" to tubs, kitchen sinks and the washer — then adds the drop-ear elbows, angle stops and fittings each line needs at its stub-out, plus hot-side insulation and support clamps. Adjust pipe type, run lengths and pressure in advanced options to match your house's actual layout.
Step by step
A step-by-step walkthrough to go with your plan above. Follow the product instructions and any local code or permit requirements as you work.
List every hot and cold connection in the house — each toilet, lav, tub/shower, kitchen sink, dishwasher and washer — and use the calculator to convert that into trunk size, port counts and branch footage before you buy anything.
Kill the main shutoff and the water heater supply, then open the lowest fixtures in the house to drain the existing lines completely before cutting into anything. Cap the old system as you disconnect it so hot and cold can't cross-connect mid-job.
Install the cold and hot manifolds in a central, accessible location — a mechanical closet or basement ceiling bay works well — close enough to the water heater and main to keep trunk runs short.
Connect the cold manifold to the main supply and the hot manifold to the water heater outlet with the sized trunk tubing, securing it with support clamps every 32 inches along the run.
Run one continuous line per port from the manifold straight to each fixture location, drilling stud and joist bays as needed. Label each line at the manifold as you go — untangling unlabeled coils later wastes hours.
Fasten a drop-ear elbow to blocking at each fixture location, connect the branch line into it, and thread on a multi-turn angle stop so the fixture has its own dedicated shutoff.
Slide foam sleeves over the hot branch and hot trunk runs before they're buried in a wall, and confirm every run — hot and cold — is clamped and can't sag or rattle against framing.
Cap or valve off every line and bring the system up to test pressure, checking each manifold port and stub-out for leaks. Only close drywall or flooring once every line has held pressure for the inspection window your code requires.
Equip the job
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Keep planning
Interior & Finishing
Answers
A home-run system runs a dedicated PEX line from a central manifold straight to every fixture, instead of branching a shared trunk line off with tees at each fixture the way copper or trunk-and-branch PEX does. It uses more total tubing, but every joint sits at the manifold or the fixture, not buried in a wall — so a leak means shutting one valved port, not opening drywall to find a hidden tee. It's also the layout that lets each branch be balanced and shut off individually.
Each fixture is assigned a supply fixture unit (WSFU) value — a toilet, lavatory, tub/shower, kitchen sink and washer all draw differently — and the calculator totals them and runs that total through a simplified version of the plumbing code's demand chart to pick a trunk diameter, from 3/4" up to 2". That's a fixture-count and demand solve, not a floor-area or fixture-count-alone divide, which is why a house with more low-flow fixtures (toilets, lavs) can need a smaller trunk than one with fewer but higher-draw fixtures (tubs, a washer).
Every fixture connection is its own port — a toilet needs one cold port, a tub/shower needs one hot and one cold — so port count is fixture count times connections, split across a dedicated cold manifold and a dedicated hot manifold. Past roughly two dozen total home-run lines, running everything back to one manifold location gets impractical to route and balance; splitting into a second manifold station, often one per floor, keeps runs shorter and the wall cavity manageable.
PEX-A uses an expansion tool to stretch the pipe over a fitting, which then shrinks back to grip it — it's more forgiving of imperfect cuts and works in tighter spaces since there's no crimp ring to clear, but the expansion tool costs more upfront. PEX-B uses a crimp ring compressed onto the fitting with a crimp tool and needs a go/no-go gauge check on every joint, but the tools are cheaper and the technique is simpler to learn. Both are code-approved in most jurisdictions; check local rules before you commit to one.
It's not universally required, but it's worth doing on any run longer than a few feet: insulating the hot branch and trunk lines cuts standby heat loss between the water heater and the tap, shortens the wait for hot water to arrive, and reduces condensation dripping inside a wall cavity in humid climates. Some energy codes require it on hot lines above a minimum diameter or in unconditioned spaces like a crawlspace — check what applies before you skip it to save a few dollars.
A home-run PEX system is genuinely more DIY-accessible than sweating copper, since there's no torch and the expansion or crimp connections are quick to learn and easy to pressure-test before covering. That said, most jurisdictions require a permit and a rough-in inspection for a whole-house repipe, and getting the manifold sizing, venting and backflow protection wrong can fail that inspection or create a real safety issue — many owners do the pulling and connections themselves but bring in a licensed plumber for the water heater tie-in and final inspection.