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Residential Plumbing Rough-In Pipe Sizes
Standard pipe sizes for common fixtures per IPC/IRC code.
| Fixture | Drain Size | Vent Size |
|---|---|---|
| Toilet (water closet) | 3" (4" for building drain) | 2" |
| Lavatory (bathroom sink) | 1-1/2" | 1-1/4" |
| Kitchen sink | 1-1/2" or 2" | 1-1/2" |
| Bathtub | 1-1/2" | 1-1/2" |
| Shower | 2" | 1-1/2" |
| Washing machine | 2" | 1-1/2" |
| Dishwasher | 1-1/2" (via disposal or tailpiece) | Via sink vent |
| Floor drain | 2" or 3" | 1-1/2" |
Plumbing Rough-In Costs by Fixture (2026)
Typical labor + material costs for residential rough-in work. Ranges vary by region and complexity.
| Fixture | Rough-In Cost |
|---|---|
| Toilet | $350 - $600 |
| Bathroom sink | $300 - $500 |
| Bathtub / shower | $500 - $1,000 |
| Kitchen sink | $400 - $700 |
| Washing machine | $350 - $600 |
| Dishwasher | $150 - $300 |
| Full bathroom (3-piece) | $1,500 - $3,000 |
| Gas line to water heater | $300 - $600 |
12,800+ estimates calculated this month
Last updated: 2026-04-06
What Actually Fails a Plumbing Rough-In Inspection
I've been on jobsites for 20+ years watching plumbers work, and the rough-in is where the real skill shows. Anyone can glue PVC together. Getting every pipe sized right, sloped right, vented right, and supported right so it passes inspection on the first try - that's the difference between a plumber and someone who owns pipe wrenches.
This checklist covers 37 items across 6 categories, organized the way the work actually flows: prep, DWV, venting, supply, gas, and then testing. I built it because I've seen too many rough-ins fail inspection over things that should have been caught before the inspector showed up. A missed vent connection, a drain with no slope, a toilet flange set to the wrong height. Each one of those costs a half-day callback and pushes the drywall schedule.
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Top 5 Rough-In Inspection Failures
These are the items I've seen fail inspection most often on residential projects:
- Wrong drain slope. Too flat and waste backs up. Too steep and water outruns solids. The inspector will check every horizontal run with a level. 1/4 inch per foot is your target.
- Missing or undersized vents. Every fixture needs a vent. If the trap-to-vent distance exceeds code limits, the trap seal siphons out and sewer gas enters the building. The inspector will trace every vent path.
- Toilet flange at wrong height. The flange must sit on top of the finished floor. If tile is going down later and the flange is set to subfloor height, the wax ring won't seal. This one gets missed constantly on remodels.
- Failed pressure test. A single drip at one fitting fails the entire system. Test before the inspector arrives. Fix your leaks on your time, not on inspection day.
- Wrong fittings for direction changes. Short-radius 90-degree fittings (vent 90s) are only for vent lines. Using them on drain lines causes blockages. Use long-sweep 90s or two 45-degree fittings for horizontal DWV turns.
Plumbing Rough-In Material Costs (2026)
| Material | Cost per Linear Foot | Common Use |
|---|---|---|
| PVC (Schedule 40) | $0.50 - $3.00 | DWV drain and vent lines (1-1/2" to 4") |
| ABS | $0.60 - $3.50 | DWV (common in Western states) |
| PEX (1/2") | $0.40 - $0.80 | Hot and cold water supply |
| PEX (3/4") | $0.60 - $1.20 | Main supply runs, manifolds |
| Copper (1/2" Type L) | $2.50 - $4.50 | Water supply (required in some jurisdictions) |
| Black iron (3/4") | $2.00 - $4.00 | Natural gas piping |
| CSST (flex gas) | $2.00 - $5.00 | Gas piping (faster install, requires bonding) |
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How to Use This Calculator
Start with pre-rough-in prep
Review approved plans, confirm fixture rough-in dimensions, and mark all drain and supply locations on the subfloor and studs before running any pipe.
Work through DWV, venting, and supply
Expand each category and check off items as you complete them. Tap the detail arrow for code references, pipe sizes, and field notes on each task.
Pressure test all systems
Fill the DWV system with water or air and pressurize supply lines per local code. Check every joint before scheduling inspection.
Photograph and schedule inspection
Document all rough-in work with photos before closing walls. Print the checklist or share it with the inspector and project lead.
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Frequently Asked Questions
What is plumbing rough-in?
Plumbing rough-in is the phase where all drain, waste, vent (DWV), and water supply pipes are installed inside walls, floors, and ceilings before drywall goes up. It happens after framing and before insulation. The rough-in must pass a building inspection before walls can be closed. Rough-in typically accounts for 60-70% of the total plumbing labor on a residential project.
How much does plumbing rough-in cost?
Plumbing rough-in for a full bathroom (toilet, sink, tub/shower) costs $1,500 - $3,000 for labor and materials. A half bath runs $800 - $1,500. A complete new-construction home with 2 bathrooms, a kitchen, and a laundry room typically costs $8,000 - $15,000 for rough-in plumbing. Remodel rough-in runs higher because of demolition, rerouting, and working around existing structure.
What size pipe is used for toilet rough-in?
Toilets use a 3-inch drain line from the closet flange to the main building drain (which is typically 4 inches). The vent is 2 inches. The water supply stub-out is 3/8-inch or 1/2-inch cold water only. The closet flange must sit on top of the finished floor, not the subfloor, so account for tile or flooring thickness when setting the flange height.
What is the correct slope for drain pipes?
The minimum slope for 3-inch and 4-inch drain pipes is 1/4 inch per foot (IRC P3005.3). For 2-inch and smaller pipes, the minimum is 1/4 inch per foot as well, though some jurisdictions allow 1/8 inch per foot for pipes 3 inches and larger. Too little slope causes waste to sit and clog. Too much slope (over 1/2 inch per foot) causes liquids to outrun solids, which also causes clogs.
What is the difference between a vent and a drain?
A drain carries waste water downhill to the sewer by gravity. A vent carries air upward to the roof to equalize pressure in the drain system. Without vents, drains create a vacuum when water flows, which siphons the water out of P-traps and lets sewer gas into the building. Every plumbed fixture needs both a drain connection and a vent connection.
How long does a plumbing rough-in take?
A standard bathroom rough-in takes 4-8 hours for an experienced plumber. A full single-family home (2-3 bathrooms, kitchen, laundry) takes 2-4 days. Remodels take longer because of demolition and working around existing pipes. The rough-in inspection itself adds another day of wait time in most jurisdictions, so plan accordingly before scheduling drywall.
What do plumbing inspectors look for during rough-in?
Inspectors check: pipe sizes match the approved plans, slope is correct on all drain lines, venting is properly connected and sized, pressure test passes (water test or air test with zero leaks), all connections use approved fittings, pipes are properly supported, and fire-stopping is in place where pipes penetrate fire-rated assemblies. A failed inspection means fixing the issue and rescheduling, which adds days to the project.
Can I use PEX for plumbing rough-in?
Yes. PEX (cross-linked polyethylene) is approved for water supply lines in all 50 states and most jurisdictions. It is faster to install than copper, costs 25-40% less in materials, and resists freezing better. PEX cannot be used for DWV (drain/waste/vent) lines. For DWV, use PVC, ABS, or cast iron depending on your local code. Some jurisdictions still require copper for the first 18 inches from the water heater.
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