Intro

Plumbing rough-in sets the whole job up for success. When your lines are straight, slopes are right, and vents make sense, final fixtures go in smooth. This guide shows you how to plan, lay out, and test plumbing so you pass inspection the first time. We’ll cover pipe sizing basics, drain slopes, vent rules, and pressure tests. You’ll also get layout heights, clearances, and timeframes you can use today. It’s written for busy crews who want clear steps, not guesswork. Use it to train helpers, check your work, and avoid callbacks.

Quick Answer

Plumbing rough-in means installing drains, vents, and water lines to code before drywall. Set correct slopes (commonly 1/4 in per foot for 2 in and smaller), place vents within allowed distances, and pressure test at 100 psi for 15 minutes. Label, photo-document, and prep for inspection to pass first try.

Table of Contents

• Key Takeaways
• Plan Your Plumbing Rough-In
• Code Checks And Materials That Pass Inspection
• Install Drains And Vents (Plumbing)
• Run Water Supply Lines (Plumbing)
• Pressure Test And Inspection Prep
• Layout And Noise Control Tips
• Paperwork That Wins The Job
• Handover And Closeout
• Questions Contractors Ask

Key Takeaways

• Set drain slopes right: 1/4 in per foot (≤2 in), 1/8 in per foot (≥3 in).
• Keep toilets at 12 in rough-in from finished wall; shower drains usually 2 in.
• Pressure test at 100 psi for 15 minutes; document with photos and labels.
• Support pipes every 4–6 ft and use nail plates at 1-1/2 in cover.
• Most bathrooms rough-in in 6–10 hours with a two-person crew.

Plan Your Plumbing Rough-In

Good plumbing starts with a simple plan. Walk the space with the drawings and fixture list. Mark centre lines on floors and studs.

1. Measure clearances.
   • Toilets: 12 in from finished wall to flange centre, 15 in min side clearance.
   • Tubs: set spout 4–6 in above rim; shower head at 78–84 in.
   • Lavs: drains at 18–20 in above floor; supplies at 20–24 in.
2. List penetrations. Note every floor and stud hole. Keep 2 in from stud edges.
3. Choose routes. Short, straight runs save time. Stack vents when possible.
4. Schedule. A standard 3‑piece bath rough-in often takes 6–10 hours. A whole-house on a two-storey may take 2–3 days.

Tip: If you’re also looking to streamline professional proposals, see our internal guide on professional proposals and scope clarity.

Code Checks And Materials That Pass Inspection

Plumbing code varies by province, but many follow the National Plumbing Code of Canada. Always verify local amendments. Here are common field checks:

• Slope: 1/4 in per foot for 2 in and smaller, 1/8 in per foot for 3 in and larger.
• Trap arms: keep within allowed vent distance. Commonly 1.5–2.5 m depending on pipe size. Check your local table.
• Venting: avoid flat vents below flood level. Keep vents vertical until 6 in above flood rim.
• Pipe: PVC or ABS for DWV; PEX or copper for water. Don’t mix ABS/PVC without an approved transition coupling.
• Supports: every 4–6 ft on horizontals, at each floor/ceiling penetration, and within 12 in of traps.
• Firestopping: seal rated walls and floors after inspection photos, before close-up.

Material choices:

• PEX is fast, flexible, and quiet. Use 3/4 in trunks, 1/2 in branches for typical fixtures.
• Copper is durable and neat. Sweat carefully and protect from corrosion.

Install Drains And Vents (Plumbing)

Work drains and vents first. It sets your plumbing elevations for everything else.

1. Snap lines. Mark main drain centres on floors. Mark wall centres at 48 in height for reference.
2. Set the main drain. Aim for straight runs. Keep cleanouts accessible.
3. Branch to fixtures.
   • Toilets: 3 in minimum branch to a 2 in vent (local rules vary).
   • Showers: 2 in drains are common. Centre in the stall for easy slope.
   • Lavs: 1-1/4 or 1-1/2 in trap, 1-1/2 in drain to 1-1/2 or 2 in vent.
4. Keep slope consistent.
   • 1/4 in per foot for 2 in and smaller.
   • 1/8 in per foot for 3 in and larger.
5. Vent smart.
   • Rise vertical to 6 in above the flood rim before going horizontal.
   • Wet vent only where allowed. Bathrooms often allow it when sized right.
6. Test fit traps and set trap arms short and straight.

Common mistake: Rolling a wye too flat. Keep the branch above the spring line so it drains and vents correctly.

Run Water Supply Lines (Plumbing)

Once DWV is set, rough the water lines. Keep lines out of exterior walls where freezing is a risk.

1. Sizing basics.
   • Typical: 3/4 in main trunks; 1/2 in branches to most fixtures.
   • Long runs or multiple heads may need upsizing. Check pressure loss charts.
2. Layout heights.
   • Lav supplies: 20–24 in above floor, 4–6 in left/right of drain.
   • Toilet stop: 6–8 in left of centreline, 6–8 in above finished floor.
   • Shower head: 78–84 in; mixing valve: 42–48 in to centre.
3. Protect lines.
   • Drill centred holes. Leave at least 1-1/2 in wood cover for nail plates.
   • Sleeve through concrete. Insulate where needed.
4. Manifolds vs tees.
   • Manifolds reduce joints and balance pressure. Tees are simple and cheap. Choose what fits the job.

Tip: Label every stub-out with room, fixture, and pipe size. It saves 30–60 minutes during trim.

Pressure Test And Inspection Prep

Don’t skip testing. It’s how plumbing passes the first time.

1. Water test supplies.
   • Pressurize to 100 psi for 15 minutes (many inspectors accept this). Fix leaks, retest.
2. Air test DWV (where allowed).
   • Commonly 5–10 psi for 15 minutes. Use approved test balls and caps. Soap every joint.
3. Seal and secure.
   • Cap all open lines. Strap within 12 in of each valve and trap.
4. Document.
   • Take clear photos of every wall before close-up. Tag the photos by room.
   • Create a one-page checklist: slopes, vent distances, support spacing, firestopping.

Pro move: Bring a hand pump gauge and a spare test ball. No delays if one fails.

Layout And Noise Control Tips

Quiet plumbing makes happy clients.

• Arrestors: Add water hammer arrestors near quick-close valves (dishwashers, clothes washers).
• Support: Strap every 4–6 ft horizontally and every floor level vertically. No pipe-on-metal contact.
• Fittings: Use two 45s instead of a hard 90 where space allows. Flow is smoother.
• Insulation: Wrap pipes through bedrooms and studies. It cuts fixture noise.
• Avoid tight holes: Leave 1/8–1/4 in clearance through studs and plates. Use grommets.

This pairs well with understanding project timelines so you coordinate with framing, HVAC, and electrical.

Paperwork That Wins The Job

Clean plumbing is only half the job. Clean paperwork wins you the work and keeps cash flowing.

Include in your proposal:

• Clear scope (rough-in + trim) and what’s excluded (tile, patching, permits if not included).
• Fixture list by brand/SKU or allowance amounts (e.g., $1,200 shower kit).
• Schedule: example, 1 day demo, 1 day rough-in, 1 day test/inspection.
• Price breakdown: labour, materials, allowances, and change order rates.
• Payment terms tied to milestones (rough-in complete, inspection passed, trim set).

Tools like Donizo help here. You can speak your site notes with Voice to Proposal, send a branded PDF via client portal, collect an e‑signature, and convert the accepted proposal to an invoice in one click. If you’re refining invoice templates or pricing strategies, see our internal resources on invoice templates and pricing strategies.

Handover And Closeout

Finish strong. It reduces callbacks.

• Label shutoffs at sinks, toilets, and the main.
• Leave a one-page homeowner guide: how to shut off water, how to clean aerators, and who to call.
• Photo the final install. Attach to the job file.
• Send the final invoice and warranty terms the same day trim is complete.

Conclusion

Solid plumbing rough-ins follow simple rules: right slopes, smart vents, solid supports, and a clean test. Do those, and you pass inspections and finish faster. Next steps:

• Walk your next job and mark every centre and height.
• Set slope lines and vent routes before cutting a single hole.
• Build a one-page test and photo checklist for every job.

For smoother client approvals and faster pay, platforms such as Donizo let you turn site notes into proposals, collect e‑signatures, and invoice in one workflow. Keep it simple, keep it neat, and your plumbing will speak for itself.