Quick answer
Plumbing rough-in is the stage of a build or remodel when the hidden pipes are installed and tested: drains, vents, water supply lines and fixture stub-outs are run through the framing or under the slab, before walls, floors and fixtures go in.
The same word names a measurement. A “12-inch toilet rough-in” is the distance from the finished wall to the center of the toilet drain. Both meanings meet at the rough-in inspection, where an inspector sees the open pipes and their test.
Quick facts
The key facts about Plumbing Rough-In, with sources:
- Happens
- After framing, before insulation and drywall; underground piping before the slab is poured 13
- Drain test (UPC, Washington checklist)
- 10-foot water head or 5 psi air for 15 minutes 1
- Water supply test
- Working pressure or 50 psi for 15 minutes 1
- Common toilet rough-in
- 12 inches; 10- and 14-inch models exist 5
- Toilet side clearance (UPC 402.5)
- 15 inches to center, 21 inches clear in front 1
Key takeaways
- Rough-in is the open-wall stage: every pipe that will be hidden gets installed, tested and inspected.
- It usually comes in parts: underground piping before the slab, then above-ground drains, vents and supply lines.
- Drain and vent pipes are filled with water or air and must hold for 15 minutes without a leak.
- Fixture rough-in dimensions, such as a 12-inch toilet, decide which fixtures will fit later.
- Nothing gets covered until the inspector passes the rough-in; covering early can mean opening walls.
What rough-in means: a build stage and a measurement
The stage. On a new home or a gut remodel, the plumber works while studs and joists are bare. They run the drain-waste-vent system, the hot and cold supply lines, and short stub-outs where each fixture will connect.
A Washington jurisdiction checklist built on the 2021 UPC and IRC lists what must be ready before the rough-in inspection, from pipe supports and nail plates to vent heights and tests 1.
The dimension. Fixture makers and plumbers also say “rough-in” for where a pipe must land.
Kohler describes the standard toilet rough-in as 12 inches, measured between the wall and the outlet pipe, and sells 10- and 14-inch models for other layouts 5.
Sinks, showers and tubs have their own rough-in heights set by the fixture’s spec sheet.
The two meanings connect. If the drain is roughed in at the wrong spot, the fixture bought later will not fit, and the fix means opening the floor.
Rough-in vs trim-out
Rough-in is the hidden piping. Trim-out (finish) is the visible part that comes after drywall: toilets, faucets, valves’ trim and appliances. Each gets its own inspection in most places.
How rough-in plumbing proceeds
Exact names vary by jurisdiction. Inverness, Florida, splits it into a first and second rough; the Washington checklist groups it by system 31.
- Underground. Drain lines and any water lines under the slab go in the trench. The Washington checklist requires a firm bed, sleeves through concrete, and brazed copper joints under a slab 1.
- Underground test and inspection. The buried drains are water- or air-tested and seen by the inspector before backfill or concrete 1.
- Drain and vent framing work. Above-floor drains, trap arms and vents are run through the studs, with vent pipes rising at least 6 inches above the flood rim before turning horizontal under UPC 905.3 1.
- Water supply. Hot and cold lines are run to each stub-out, with water hammer arrestors where quick-closing valves will be used 1.
- Protection. Nail plates go where pipe is within 1 inch of the stud face, and outside-wall pipes get freeze protection 1.
- Test and inspect. Drains, vents and supply lines are put under test and left for the inspector 12.
- Underground drainsBefore the slab
- Underground testInspector sees it open
- DWV through framingDrains, trap arms, vents
- Supply lines and stub-outsHot, cold, arrestors
- Rough-in test and inspectionThen insulation and drywall
Which rough-in dimensions each fixture needs
| Fixture | Rough-in point | Rule or typical value |
|---|---|---|
| Toilet | Wall to center of drain | 12 inches standard; 10 and 14 available 5 |
| Toilet | Side and front clearance | 15 inches center to side wall, 30 inches total width, 21 inches in front (UPC 402.5) 1 |
| Toilet | Drain to vent distance | Closet ring to vent no more than 6 feet (UPC Table 1002.2) 1 |
| Shower | Valve type and size | Listed pressure-balance or thermostatic valve, 120°F max; at least 900 square inches with a 30-inch circle (UPC 408) 1 |
| Washer box | Standpipe and trap | Standpipe 18 to 30 inches above the trap; trap weir 6 to 18 inches above the floor (UPC 804.1) 1 |
| Kitchen sink | Dishwasher drain | Approved air gap fitting on the discharge (UPC 807.3) 1 |
| Any fixture | Fixture outlet to trap | No more than 24 inches vertical (UPC 1001.2) 1 |
Example: checking a bathroom rough-in before drywall
A worked check of one bathroom against the Washington UPC checklist 1. The layout numbers are illustrative; the limits are the checklist’s.
| Item | As built (illustration) | Checklist limit | Result |
|---|---|---|---|
| Toilet drain from finished back wall | 12 in | Match the toilet; most are 12 in 5 | Fits a standard toilet |
| Toilet center to vanity side | 16 in | At least 15 in (UPC 402.5) | Pass |
| Clear space in front of toilet | 24 in | At least 21 in (UPC 402.5) | Pass |
| Lavatory trap arm, 1-1/2 in pipe | 48 in to vent | At most 42 in (UPC Table 1002.2) | Fail: move the vent closer |
| Drain test | Water to 10 ft head, 15 min | 10 ft head or 5 psi air, 15 min (UPC 712) | Pass if no drop or drip |
| Supply test | Working pressure, 15 min | Working pressure or 50 psi, 15 min (UPC 609.4) | Pass if the gauge holds |
The trap arm failure is cheap to fix now and costly after tile. That is the whole point of a rough-in inspection.
Where rough-in shows up on permits, schedules and spec sheets
On a contractor’s schedule or draw. Builders bill and schedule by stage, so “rough plumbing complete” is often a payment milestone.
On the permit card. Inspections are listed as rough-in (or first and second rough) and final 3. Washington’s checklist asks that the permit and approved plans be on site for the inspector 1.
On a test form. Some towns ask the plumber to certify each test. The Town of Ramapo, New York, form lists drain and vent water and air tests, water supply, sewer and shower pan tests, each held 15 minutes, with the plumber’s license number 4.
On a fixture box or spec sheet. Toilets list their rough-in size; check it before you buy 5.
What a good rough-in protects, and what it cannot fix
What a good rough-in gives you
What it cannot fix
- Wrong fixture choices made after rough-in; a 10-inch toilet will not suit a 12-inch drain without an offset.
- Damage after inspection, such as a nail through a pipe without a nail plate.
- Problems in parts not roughed in, such as the old sewer line on a remodel.
- Poor water pressure from the street; that is a supply issue, not a rough-in one.
What a passed rough-in does not prove
A rough-in pass means the pipes held a test and met code on the day the inspector looked, but it says nothing about fixtures, the water heater or how the system performs once water is flowing, because those are checked at final.
Tests also have limits. The Washington checklist bans air tests on plastic drain pipe and allows air on plastic supply only for PEX, per the maker, when freezing is a risk 1. A short 15-minute test finds open joints, not slow seeps that show up over weeks.
What drives the cost of rough-in plumbing
We do not print prices; fair numbers need dated local quotes.
Rough-in cost follows the number of fixtures, how far each is from the main stack, the pipe materials, whether work is under a slab, and access.
Moving a toilet or shower on a slab means cutting concrete; on a raised floor it may not.
Permit and inspection fees, re-inspection after a failed test, and an extra vent through the roof all add.
Our plumbing cost guide explains how quotes are built. For layout sizing, the fixture unit calculator shows how fixture count drives drain size.
Who does the rough-in and how the inspection works
- Permit. A licensed plumber is listed on the permit in Washington unless the homeowner does their own plumbing 1. Rules on homeowner work vary by state and city.
- Layout. The plumber marks fixture centers from the plans and the chosen fixtures’ spec sheets.
- Install. Drains, vents and supply lines go in with supports, sleeves and nail plates 1.
- Test. Drains and vents are filled to a 10-foot head or held at 5 psi air for 15 minutes; Michigan’s amended rule says the same for IRC-based work 21.
- Inspection. The inspector checks the test, materials, sizing and clearances, then signs the permit card or leaves a correction list 3.
- Cover. Only then do insulation and drywall go on.
Test pressure is not a DIY experiment
Air tests store energy; a cap or plug that blows off can injure. The Washington checklist bans air testing of plastic drain pipe 1.
Leave testing to the plumber, stay clear of capped pipe under test, and keep the water off at the main until the plumber says the system is ready.
Gas piping has its own test and must be done by a licensed pro.
How to protect rough-in work until trim-out
- Keep test caps and plugs in place so debris and drywall mud stay out of drains.
- Photograph every wall before drywall with a tape measure in view, because those photos show where each pipe runs long after you have forgotten, and they save guesswork when you later drill for a shelf, a grab bar or a TV mount.
- Check nail plates are still on after electricians and HVAC crews finish 1.
- In cold weather, keep heat on or drain lines that could freeze; the checklist calls for freeze protection outside the heated space 1.
- Tell your plumber before changing a fixture model; its rough-in may differ.
Which rough-in problems need a plumber
- A failed test with water dropping in the stack or a gauge losing pressure.
- A toilet drain that measures off from the toilet you bought.
- A trap arm longer than the code table allows, or vents that turn flat too low 1.
- Pipes bored too close to the stud face with no nail plate 1.
- Drains with too little slope or sags between hangers.
- Walls closed before the inspection, which can mean opening them again.
For remodels, our fixture installation service covers moving or adding fixtures. How to choose a plumber covers license and permit questions to ask.
Which codes set rough-in tests and clearances
Model codes. Most states adopt either the International Residential Code (with the International Plumbing Code) or the Uniform Plumbing Code, often with amendments. Test sections in the IRC are numbered P2503; a New York form cites RCNYS P2503.5.1, P2503.5.2 and P2503.7 for drain water, drain air and water supply tests 4.
Washington (UPC 2021 with state amendments). A March 8, 2024 checklist lists drain tests under UPC 712, supply tests under UPC 609.4, toilet clearances under UPC 402.5, and trap arm lengths under UPC Table 1002.2 1.
Michigan (IRC with state rules). Mich. Admin. Code R 408.30533a, effective August 29, 2025, amends P2503.5.1: drains and vents must hold a 10-foot water head or 5 psi air for 15 minutes after rough piping is in place 2.
Florida. Inverness requires a 10-foot head on drains and vents at first rough, a 5-foot head on the building sewer for 15 minutes, and a supply test at working pressure, under the Florida Building Code 3.
These are examples, so check the code edition and amendments your city or county enforces before work begins. The figure below pulls together the test numbers that repeat across all four documents.
Model code vs local rule
Code numbers here come from public state and city copies. ICC’s own code site blocked automated retrieval on 2026-10-13, so we cite adopted versions rather than the base model text.
How rough-in differs from underground, trim-out and final
| Stage | What happens | Inspection |
|---|---|---|
| Underground | Buried drains and supply under the slab or in the trench 1 | Before backfill or pour |
| Rough-in | Drains, vents, supply lines and stub-outs in open walls 1 | Before insulation and drywall |
| Pressure test | Water or air test of the rough-in piping 2 | Part of rough-in |
| Trim-out / final | Fixtures, faucets, water heater set and working | Final inspection |
| Inspection report | Written findings on an existing system | Not a code inspection |
Which rough-in beliefs are wrong
- Myth Every toilet fits every bathroom.
- Reality Toilets come in 10-, 12- and 14-inch rough-ins; 12 is the most common 5.
- Myth A dry rough-in is fine; you will see leaks later.
- Reality Codes require the pipes to hold a test before they are covered 21.
- Myth Air testing is always faster and fine.
- Reality The Washington checklist bans air tests on plastic drain pipe 1.
- Myth The inspector checks fixtures at rough-in.
- Reality Fixtures are checked at final; rough-in covers the hidden piping.
How your location changes rough-in
Climate and code adoption both matter. Washington’s checklist requires water service at least 12 inches below the local average frost level and R-3 insulation on lines outside conditioned space 1.
Florida’s Inverness checklist sets a 12-inch minimum depth below grade for water service 3. Western states such as Washington use the UPC, while Michigan and New York use IRC-based rules 124. Ask your building department for its rough-in checklist; many publish one.
When rough-in should change your fixture choices
Pick fixtures before rough-in, not after, because the toilet’s rough-in size, the shower valve brand and the vanity’s drain height all decide where the pipes land. Changing your mind on paper costs nothing, while changing it after drywall means cutting walls or floors.
On a remodel, ask whether the plan moves any drain. Moving a drain on a slab or far from the stack is the biggest rough-in cost lever, and the place to ask for options.
- If Fixtures not chosen yet
- Then Choose them now and give the plumber the spec sheets
- If Toilet replacement only
- Then Measure wall to bolt center: 10, 12 or 14 in 5
- If Drain moves on a slab
- Then Expect concrete cutting; ask for options
- If Inspection not booked
- Then Do not let walls close
- If Test failed
- Then Fix and retest before cover
Source: [5]
Questions about Plumbing Rough-In
What is included in a plumbing rough-in?
Everything that will be hidden: drain and waste pipes, vent pipes, hot and cold supply lines, stub-outs for each fixture, and items like water hammer arrestors and nail plates. Underground piping under a slab is usually its own earlier step. Fixtures, faucets and the water heater come later at trim-out.
What is the standard toilet rough-in?
Twelve inches, measured from the finished wall behind the toilet to the center of the drain. Kohler calls 12 inches the standard and also sells 10- and 14-inch models. Measure to the center of the floor bolts if the toilet is still in place, and buy a toilet that matches.
How long does a rough-in plumbing test have to hold?
Fifteen minutes in the checklists we reviewed. Drains and vents are filled to a 10-foot water head or held at 5 psi air for 15 minutes, and water supply lines at working pressure or 50 psi for 15 minutes. Michigan’s rule and a Washington UPC checklist both use these figures.
When does the rough-in inspection happen?
After the pipes are installed and under test, but before insulation, drywall or concrete hide them. Many jurisdictions also inspect underground piping separately before backfill. The inspector signs off or leaves a correction list, and walls stay open until it passes.
Can I close the walls before the rough-in inspection?
No. The inspector must see the piping and its test. Covering it early can lead to an order to open the walls. If the inspection is delayed, protect the open work and keep the schedule on hold rather than hanging drywall.
How far should a toilet be from the wall and other fixtures?
Under UPC 402.5, as listed on a Washington checklist, a toilet is set at least 15 inches from its center to a side wall, with 30 inches total clear width and 21 inches clear in front. IRC-based codes use similar figures. Check your local code, since some amend these numbers.
What is the difference between first rough and second rough?
Some jurisdictions split rough-in into two visits. In Inverness, Florida, first rough covers water service and underground work, and second rough covers drains, vents, cleanouts and fixture spacing, with tub and shower pan tests. Other places use one rough-in inspection plus an underground one.
Can a homeowner do their own rough-in plumbing?
In some places, on their own home, with a permit. Washington’s checklist expects a licensed plumber on the permit unless the homeowner is doing the work. Many cities limit or bar homeowner plumbing. Ask your building department before starting, and expect the same inspection and tests.
What happens if a rough-in test fails?
The plumber finds the leak, fixes the joint or fitting, and runs the test again. The inspector then returns for a re-inspection, which may carry a fee. Failing at rough-in is normal and far cheaper than a leak found after the walls are finished.
Sources
- MyBuildingPermit.com, Inspection Checklist: Residential Plumbing Rough-In (2021 IRC/UPC with Washington amendments, March 8, 2024), retrieved .
- Mich. Admin. Code R 408.30533a, Rough plumbing (effective August 29, 2025; Cornell LII copy), retrieved .
- City of Inverness, Florida, First Rough and Second Rough Plumbing Inspection Checklist, retrieved .
- Town of Ramapo, New York, Plumbing Test Certification Form (RCNYS P2503, PCNYS 312), retrieved .
- Kohler / Sterling, Toilet brochure (manufacturer; rough-in sizes), retrieved .
Expert review
Written by the HyrePlumber Research team. Not yet reviewed by an outside expert. We say so rather than imply a review that has not happened; see our editorial policy.
How the numbers were checked: Test pressures, durations, clearances, trap arm lengths and stage requirements are taken from published jurisdiction documents: a 2021 UPC/IRC Washington checklist, Michigan’s amended rough plumbing rule, an Inverness, Florida checklist and a Ramapo, New York test form.
Toilet rough-in sizes are from a single manufacturer’s brochure (Kohler). Base ICC model code text could not be retrieved; readers are told to check their adopted edition. The bathroom example uses illustrative layout numbers against sourced limits. No prices are given.
Suggest a correction. We fix errors and say what changed.