How I’d actually use this on a flip
On a Chicago-metro deal, I run the gut rehab calc first to decide whether the property pencils overall. If the plumbing line on that breakdown is more than ~10% of hard cost, I drop into this calc and tighten the number. Square footage from the listing, fixture count from the floorplan, bath count from the photos, and I default the supply material to PEX-A until I see something in the basement that changes my mind. Leak flags stay off until the walkthrough.
Second pass is during the walkthrough. I put hands on the supply stubs at the water heater and at any exposed basement run. Gray, threaded, magnetic with a screwdriver tip stuck to it — that’s galvanized, and the calc force-promotes whatever scope I picked to full-house repipe. Gray plastic with banded fittings (especially on a 1978-95 build year) — that’s polybutylene, and the engine does the same. Either flag flipped, and I’m re-baselining the deal on a 5-figure repipe instead of a 4-figure partial. The requested-scope dollars get replaced; that’s the move competitor calcs skip, and it’s the move that turns “the listing said updated plumbing” into a number an offer can survive.
A Michigan tax-deed property I picked up two years back is the cautionary tale here. Listing photos showed copper supply at the water heater; walkthrough showed copper for the first six feet, then galvanized everywhere downstream where I hadn’t looked. Calc would’ve flagged the same scope promotion the inspector eventually did. Now I budget repipes against the calc’s high band with every supply-side flag set before I write the offer, then relax flags only on what the walkthrough actually clears.
Repipe Reality — what an inspector will catch
Five conditions that change your budget once the plumber or the inspector walks through. Each is framed as “what you see / what it means / what to do.”
- Galvanized supply lines.
What you see: threaded steel pipe at the water heater or basement ceiling, usually pre-1960 vintage. Pressure drops when more than one fixture runs.
What it means for budget:the calc auto-bumps you to full-house repipe. Galvanized fails systemically — one branch corroding through means the rest are on the same clock. Most Chicago-metro inspectors won’t sign off on partial scope. Homeowner-policy carriers increasingly flag galvanized as a non-renewal trigger.
What to do:plan full-house in your budget from the start; don’t price a partial. Combined with low-pressure history (pinhole-leak signature) or slab foundation (every leak becomes a slab-cut event), the urgency is higher. - Polybutylene (PB) supply lines.
What you see: gray flexible plastic pipe with banded metal fittings, 1978-1995 install era. PB-2110 stamping on the pipe.
What it means for budget:the calc auto-bumps you to full-house repipe. PB was the subject of the 1995 Cox v. Shell Oil Co. settlement for systemic acetal-fitting failures. Most homeowner-insurance carriers list PB as non-renewable and won’t quote without confirmed full replacement.
What to do:budget the full system from day one. Don’t try partial PB-to-PEX transitions — the joints between old and new are chronic failure points. - Cast iron drain lines.
What you see: black iron drain pipe (4-inch typical) visible in basement ceilings or crawl space. Rust-flaking or cracking on horizontal runs.
What it means for budget: warning only, no auto-promotion. If you open supply scope wide enough, the inspector may require companion drain-side replacement under UPC 609.
What to do: price drain replacement separately on the calc by enabling the drain-side flag, so the band reflects both sides. - Pre-1986 home.
What you see: copper supply with soldered joints, built before the 1986 Safe Drinking Water Act lead ban took effect.
What it means for budget:any disturbed copper joint may need lead-free-solder remediation under the SDWA 1986 amendments + EPA Lead and Copper Rule. Repair-only scope on pre-1986 commonly grows into partial-branch once the inspector arrives, so the calc auto-promotes repair-only → partial-branch. (Note: IPC 312 governs system pressure testing, not lead chemistry — lead-solder rules live with EPA / SDWA.)
What to do: assume your repair-only budget will land at partial-branch numbers; rework the spreadsheet before bidding. - Slab foundation.
What you see: concrete slab without a basement or crawl space underneath. Supply lines buried in or under the slab.
What it means for budget:the calc adds a slab-cut + repair line when scope is at partial-branch or above — each fixture access point is 2-4 sqft of slab opening at $40-90/sqft. On repair-only scope, the calc surfaces a warning instead: leak detection typically requires acoustic + thermal locate ($300-800 separately).
What to do: get the locate cost line-itemed before committing to repair-only on a slab. If multiple access points are needed, full-house often pencils better than serial slab cuts. - Low / inconsistent water pressure (no visible galvanized).
What you see:pressure drops when multiple fixtures run, but the pipe material isn’t obviously galvanized.
What it means for budget: warning only, no auto-promotion. Pressure history alone may still mean pinhole corrosion upstream. Even after a partial repipe, expect 3-6 month re-emergence risk on un-touched branches.
What to do: widen your contingency band by 10-15% on partial scope, or move to full-house if the property history suggests upstream corrosion.
Methodology
Every dollar number on this page traces to one of three layers: SiteworkMath planning ranges (anchored on Uponor / SharkBite / Apollo PEX A/B spec sheets, copper Type L mill data, CPVC manufacturer specs, MCAA labor units where citable, and Chicago-metro 2024-2026 permit fee schedules), code references (UPC 2024 §604 water distribution, §605 PEX install, §609 drain pipe; IPC 2024 §312 testing requirements, §605 backflow protection — cited inline in the inspection reality footnote), and operator calibration on Chicago-metro permit-tier behavior. The full per-cluster sourcing tier in methodology spells out which sources back which kinds of claims. The numbers are planning ranges, not contractor bids — the feasibility caveat is part of the engine output for that reason.
Show the formulas
- Supply piping:
runLengthLf × $/lf × labMult. Run length derives fromsqft × 0.3 + fixtureCount × 12on full-house; ~40% of that on partial-branch; 10 lf on repair-only. PEX A/B ~$4-9/lf combined; copper Type L ~$14-32/lf; CPVC ~$6-14/lf. Owner-with-permit multiplier 0.75× labor. - Fittings + manifold:
basePrice × max(0.5, fixtureCount/10) × labMult. PEX A/B manifold $250-700 mid base; copper soldered $700-1700 mid base (~2.5× PEX). Scales with fixture count touched. - Fixture rough-ins:
fixtureCount × $150-400 × labMult. Includes valve, drop, escutcheon, supply stub per fixture. Excludes the fixture itself. - Drain piping (conditional): Active on full-house scope, or any scope when
castIronDrainflag set. Length scales with bath count (25 lf/bath + 30 baseline). Cast iron ~$55-110/lf combined; PVC schedule 40 ~$14-28/lf. Governed by UPC 609. - Main line + ROW permit (conditional): Active onlywhen main-line scope is explicitly selected. Full-house repipe does NOT include the street / utility-side service line by default — if you need both interior repipe and main-line replacement, run the calc twice (once per scope) and add the totals. Trench length 60-150 lf typical Chicago-metro lot. $80-160/lf material+labor plus Chicago-metro ROW permit $1500-5000 fixed adder. The main-line scope surfaces a separate warning banner because the utility-side cost is jurisdictional and can’t be priced from this calc.
- Slab cut + repair (conditional): Active when
slabFoundationflag set + scope at partial-branch or above.accessPoints × 3 sqft × $40-90/sqft × labMult. Access points scale with fixture count touched (60% on full-house; 30% on partial; 1 on main-line). - Permit + inspection: fast $50-200 / typical $100-400 / strict $300-1200 mid. Strict-tier is Chicago-metro Oak Park / Evanston / Wilmette baseline (~3× typical mid).
- Confidence band: high ±10% / medium ±18% / rough ±32%, plus ±4% per active leak flag.
- Scope promotion: galvanized OR polybutylene promotes any non-full scope to full-house repipe; pre-1986 + repair-only promotes to partial-branch. Reality checks (cast iron drain, low pressure without galvanized, slab + repair-only) surface as warnings without promoting scope.
- Engine logic:
lib/sitework/plumbing/plumbing.tswith pricing anchors indefaults.tsand types intypes.ts. Tested inplumbing.test.ts.
Frequently asked
What does this plumbing repipe cost calculator estimate?
A planning-range budget for residential supply-side plumbing — the number you'd use to decide whether to walk, bid, or kill before calling licensed plumbers. Not a contractor bid. Included: plumber labor, supply pipe + fittings + fixture rough-ins, permit + inspection, drain piping when castIronDrain is flagged, slab access when slab-foundation is flagged. Excluded: the fixtures themselves (toilet, vanity, faucet), water heater replacement, drain-only scope, wall repair / patch / paint when fishing through finished drywall (budget separately at $1.50-$3/sqft), and HVAC re-routing. Sourcing detail is in the methodology section below — manufacturer install guides + MCAA labor units + UPC/IPC code references.
Why does this calculator have five scope modes instead of one repipe estimate?
Because the dollars and the inspector consequences are different across the five. Cost-guide aggregators flatten these into one page with a per-fixture or $/sqft number, which buries the question that actually matters: which scope are you allowed to do? Full-house repipe — every supply branch, manifold to fixtures. Partial branch — one zone or bathroom cluster, leave the rest alone. Main line — street-to-meter or meter-to-manifold primary supply trench. Galvanized → PEX — material conversion across all supply branches. Repair only — 5-15 lf targeted leak section. The calc returns the line set for the recommended scope and dims the rest. A galvanized system can't legally stop at partial-branch in most Chicago-metro jurisdictions — the inspector force-promotes you to full-house.
What does 'scope promoted' mean in the Inspection Reality output?
The engine returned a different scope than you asked for, because a supply-side leak flag triggered the conservative default. Galvanized supply → full-house repipe. Galvanized fails systemically; one pinhole means the next branch is on the same clock. Polybutylene (PB) → full-house repipe. PB was the subject of the 1995 Cox v. Shell Oil Co. class-action settlement (the $1.1B PB pipe program administered by the Consumer Plumbing Recovery Center, claim window closed 2009). Homeowner-insurance carriers list PB as a non-renewable risk. Galvanized + slab foundation → full-house + a slab-cut line. Galvanized + low-pressure history → full-house (textbook pinhole signature). Pre-1986 home + repair-only → partial-branch (smaller promotion). The reason is lead-free-solder remediation under the Safe Drinking Water Act 1986 amendments + EPA Lead and Copper Rule, NOT IPC 312 (which is system pressure testing, not lead chemistry). The Inspection Reality panel renders the engine's reason verbatim so you can see the rule that fired.
Why does the main-line replacement scope warn about a separate quote?
Because main-line work straddles two jurisdictions that competitor calcs flatten into one number. The street-to-meter side is municipal / utility territory — the utility either does the tap themselves or requires you to use a specific licensed contractor on their pre-approved list, and the cost is driven by their schedule and their crew rates, not the open plumbing market. The meter-to-manifold side is homeowner territory and prices like normal trench plumbing. The calc estimates the interior-side line plus the Chicago-metro ROW permit fee adder, but it cannot price the utility side without your specific utility's rate sheet. The warning banner that appears above the cost output when scope=main-line says exactly this: get a utility quote for the street-side scope before committing. Skipping that step is how main-line projects double in budget after the contract's signed.
What's the difference between this calc and a plumber's bid?
A plumber's bid prices the specific scope on the specific property with the specific access conditions; this calc prices the scope category on a typical property in your jurisdiction tier. Use the calc to decide whether the project pencils and whether to call plumbers at all. Use the bid as the actual contract number. The feasibility caveat — 'a planning estimate, not a contractor bid' — is part of the engine output for that reason. On a flip, I run this calc on the property photos before I even submit an offer, then drop into a plumber bid only after the property pencils at the calc's high band. If the calc's high band is wider than the deal can survive, walking before paying for inspections and bids is exactly what the calc is for.
What's NOT included in this calc?
Fixture choice is out of scope — this calc estimates rough-ins (valves, drops, escutcheons, supply stubs) but does not price the toilet, vanity, faucet, shower trim, or shut-off valves themselves; those vary 5-10× across consumer/builder/luxury tiers and belong on a separate fixture-budget line. Water heater replacement is out of scope; tank-to-tankless conversions are a different cluster ($3-8K typical). Drain-only scope is out — this calc is supply-side primary, with drain piping activating only when full-house scope or castIronDrain flag are set; a dedicated drain-only or sewer-only project belongs on a different surface. Wall repair / patch / paint runs outside the plumber's bid — budget separately at $1.5-3/sqft of affected wall area. Code-required water shut-off, expansion tank, pressure-reducing valve, and backflow preventer additions surface in the fittings line but not as separate calls; pull from the contingency band if your AHJ requires upgrades the engine doesn't see.
What I’d do next
- Plug this number into the gut-rehab feasibility calc
If the plumbing scope is one line on a larger rehab, take the mid from this calc and override the plumbing line on the gut-rehab cost calc.
- Sequence the repipe against demo, drywall, and inspection gates
Plumbing rough-in is gated by demo and frame inspections, and gates drywall on the back end alongside electrical. The timeline calc shows the critical-path slot.
- Read the planning-range methodology
What's anchored, what's a planning range, and how the manufacturer-spec + MCAA + permit-fee cross-check works against operator calibration.
Also in this cluster
By James Wu. Pricing anchors: Uponor / SharkBite / Apollo PEX A/B spec sheets, copper Type L mill data, CPVC manufacturer specs, MCAA labor units where citable, Chicago-metro 2024-2026 permit fee schedules. Code references: UPC 2024 §604 (water distribution sizing), §605 (PEX install), §609 (drain pipe); IPC 2024 §312 (system pressure testing), §605 (backflow protection). Lead-solder remediation on pre-1986 joints is driven by the Safe Drinking Water Act 1986 amendments + EPA Lead and Copper Rule (LCRR), not IPC 312. Engine logic in lib/sitework/plumbing/plumbing.ts. Numbers are SiteworkMath planning ranges, not contractor bids — feasibility framing is part of the output for that reason. Not a substitute for a licensed plumber’s site visit. Full methodology.