How to Estimate Plumbing Work: Rough-In, Fixture Replacement, and Repipe Pricing

Residential plumbing costs $150-500+ per fixture for rough-in (new supply and drain lines to a fixture location), $200-1,500 per fixture for replacement (removing the old and installing the new), and $4,000-15,000+ for a whole-house repipe. The enormous range reflects the gap between accessible, straightforward work and jobs that require opening walls, running through tight spaces, and repairing finishes afterward. Rough-in pricing (new lines to a fixture location): a standard bathroom rough-in (toilet, sink, tub/shower) runs $1,500-4,000 for the plumbing alone — not including the fixtures themselves. A kitchen rough-in (sink, dishwasher, possibly a gas line for the range) runs $1,000-2,500. Individual fixture rough-ins: toilet = $300-600, sink = $250-500, tub/shower = $500-1,000, laundry hookup = $300-700. These assume accessible framing (new construction or open-wall remodel). If walls are closed and you need to cut, run pipe, and patch, add 30-50% for the access work. Fixture replacement (remove old, install new): toilet replacement is $200-500 labor (the fixture itself is $100-800 depending on grade). Faucet replacement: $150-350 labor. Water heater replacement: $800-2,500 labor for a tank unit, $1,500-4,000 for tankless (including gas line and venting modifications). Garbage disposal: $150-300 labor. Bathtub replacement (including valve work): $1,000-3,000 labor. Whole-house repipe: PEX is $4,000-8,000 for a typical 2-bathroom home. Copper is $8,000-15,000+ for the same home. CPVC falls between at $5,000-10,000. The material cost difference is significant (PEX at $0.50-1.50/ft vs copper at $3-8/ft) but labor is the dominant cost — running new lines through an existing home with closed walls is slow work regardless of material. This content is for educational purposes only and does not constitute legal or financial advice.

Rough-in pricing is not just about pipe — it is about accessibility, distance, and code compliance. The same toilet rough-in that costs $300 in new construction (open framing, gravity drain directly below) can cost $800+ in a basement remodel (concrete floor that needs to be cut, possibly requiring an ejector pump if the drain is below the sewer main). Supply lines are the simpler half. PEX supply runs from the main trunk line to each fixture: typically 3/4-inch for trunk lines, 1/2-inch for individual fixture branches. PEX is the dominant material for residential new construction and remodels because it is flexible (bends around obstacles without fittings), freeze-resistant (expands without bursting), and fast to install (push-fit or crimp connections vs soldered copper joints). Material cost for supply runs: $0.50-1.50 per linear foot for PEX, $3-8/ft for copper. A typical bathroom is 20-40 feet of supply line depending on the distance from the water heater and main. Drain-waste-vent (DWV) is the expensive half. Drain pipes are larger (1.5-inch for sinks, 2-inch for showers, 3-inch for toilets, 4-inch for main drain), must maintain proper slope (1/4 inch per foot for most drain lines — this is code, not a suggestion), and require vent connections that extend through the roof. PVC is standard for DWV. The labor-intensive part: routing drain lines through existing floor joists (which often requires notching or boring, with code-mandated limits on how much you can cut from a joist), maintaining slope over long runs (which sometimes means lowering ceilings or raising floors), and connecting to the existing vent stack. The vent connection is what most DIYers and some inexperienced contractors miss entirely. Every drain fixture needs a vent within a code-specified distance (typically 5-8 feet for a 1.5-inch drain, 6-10 feet for a 2-inch drain) to prevent siphoning of the trap seal. An unvented drain gurgles, drains slowly, and can allow sewer gas into the home. Adding a vent run to an existing stack — or installing a new vent through the roof — adds $200-500 per fixture in a remodel. ContractorIQ includes plumbing rough-in calculators with fixture-count pricing, material estimators, and DWV slope verification tools.

Water heater replacement is one of the most common residential plumbing jobs and one of the most commonly underbid — because the heater itself is only part of the cost. Tank water heater replacement (like for like — same fuel, same location, same capacity): the heater costs $400-1,200 (40-gallon gas tank at $400-600, 50-gallon at $500-800, 80-gallon or hybrid/heat pump at $800-1,200+). Labor for a straightforward swap: 2-4 hours for a 2-person crew = $300-800. But here is where bids go wrong: the old unit may not meet current code. Expansion tanks are now required in most jurisdictions ($50-150 installed). Drip pans and drain lines are required if the unit is in a finished space ($75-200). Gas flex connectors may need replacement ($30-50). Seismic straps are required in earthquake zones ($30-75). Permits are required for water heater replacement in most jurisdictions ($75-200). Each of these is a $50-200 line item that is easy to forget and impossible to absorb on a competitive bid. Tankless conversion is where the real money is — and where the real estimating complexity lives. A tankless gas water heater costs $1,000-3,000 for the unit. But the installation is not just hanging the unit: the gas line almost always needs to be upsized (tankless units require 150,000-200,000 BTU, which demands a 3/4-inch gas line vs the 1/2-inch that fed the tank unit). That gas line upgrade is $300-800 depending on the run length. The exhaust venting is different — tankless units require stainless steel category III or IV vent material ($200-500) routed through an exterior wall or roof. The condensate drain (for condensing units) needs to be routed to a drain or exterior ($100-200). Electrical: most tankless units need a dedicated 120V outlet for the control board ($150-300 if one does not exist). Total tankless conversion: $2,500-5,000+ beyond the unit cost. ContractorIQ includes water heater replacement estimating templates with code-compliance checklists that prompt for every line item most contractors forget.

Plumbing estimates require more contingency than most trades because you cannot see behind walls and under floors until you open them. The pipe that looks straightforward on a plan may encounter unexpected obstacles: structural members that cannot be cut, existing pipes that are not where the plans show them, and concealed water damage that expands the scope. Permit and inspection costs: plumbing permits are required for nearly all work beyond simple fixture replacements (and even some fixture replacements — water heater, for example). Permit fees: $75-300 depending on scope and jurisdiction. The inspection typically happens before walls are closed (rough-in inspection) and after fixtures are installed (final inspection). Budget time for the inspection — it may not happen the same day you are ready for it, which means a gap in your schedule. If the inspector finds a code violation, you correct it and schedule a re-inspection, which adds a day or more. Wall and ceiling repair is the hidden cost that turns a plumbing estimate into a money pit. If you cut into drywall to access pipes, someone has to repair it. If you are a plumber, you either subcontract the drywall repair (which adds $200-500 per access point for cut, patch, tape, mud, texture, and paint) or you do it yourself (which takes time and requires competency in finishing, not just patching). Include wall repair as a line item — do not assume the homeowner will handle it. If you exclude it, make the exclusion explicit and in writing. Markup for residential plumbing: 40-55% on total cost (materials + labor + subs). Plumbing carries high liability (water damage from a failed connection can cost $10,000-50,000+ in a finished home), requires licensing and continuing education, and involves significant tool and vehicle investment. Contractors who bid at 25-30% markup are underinsured, underestimating their overhead, or losing money. The margin must account for the warranty obligation (1-2 years on labor is standard) and the callback risk inherent in pressurized water systems. Present the estimate with clear line items: fixture material (specify manufacturer and model), pipe material and linear footage, labor by task (rough-in, fixture installation, testing), permits and inspections, wall repair or exclusion note, disposal of old fixtures and materials, and any subcontracted work (gas line by a gas fitter, electrical by an electrician). A detailed estimate differentiates you from the lowball bid that says Replumb bathroom: $2,500 with no breakdown. ContractorIQ includes plumbing proposal templates with pre-built line items, code-compliance checklists, and markup calculators that help you build accurate, professional estimates.