Bathroom Plumbing Remodel Checklist: Codes, Vents, and Fixture Placement

If you’re about to tile a bathroom, this checklist can save you from the two costliest words in remodeling: tear-out. At H.I.S. Plumbing, we help homeowners pass inspections the first time by planning for code, correct venting, and manufacturer specs before walls close.

Every city reads code a little differently. That’s why we focus on the steps that matter everywhere: proper layouts, right pipe sizes, correct slopes, solid vents, watertight assemblies, and documented tests. Keep this list handy and tile with confidence.

Plan and Permit 📋

Good bathrooms start on paper. Verify layout, sizing, and inspections before the first cut.

• Layout verification

  • Sketch every fixture with centerlines and finish dimensions.
  • Check clearances: toilet side-to-side and front, shower door swing, and door/vanity conflicts.
  • Note all wall niches, benches, and grab-bar blocking.

• Fixture loads and sizing

  • Add up drainage fixture units (DFUs) for the bathroom group (toilet, lavatory, tub/shower). Your building department uses DFUs to size drains and vents.
  • Typical minimums (always verify under your adopted code: IPC or UPC):
    • Toilet (water closet): 3-inch drain, 2 DFUs (gravity).
    • Tub/Shower: 2-inch drain, 2 DFUs.
    • Lavatory: 1-1/4 to 1-1/2-inch trap with 1-1/2-inch drain, 1 DFU.
  • Water supply: confirm pipe sizes for pressure and simultaneous use. Most bathrooms run 1/2-inch branches from a 3/4-inch trunk, but long runs or multiple body sprays may need upsizing.

• Drain slope

  • Standard slope for horizontal drainage is 1/4 inch per foot for pipe 3 inches and smaller. Some codes allow 1/8 inch per foot on 4-inch and larger runs.
  • Keep slopes uniform—no bellies (sags) that hold water.

• Permits and inspections

  • Permit requirements vary by city and county. Call your local authority having jurisdiction (AHJ) to confirm.
  • Schedule rough plumbing, shower pan flood test, and final inspections early. Inspection backlogs can delay tile and fixtures.
  • If you plan to use air admittance valves (AAVs), ask if they’re allowed in your jurisdiction.

Pro tip: Bring printed cut sheets for every faucet, valve, and fixture to your rough inspection. Inspectors appreciate when marks on studs match manufacturer specs.

Rough-In Essentials 🔧

Here are the rough-in dimensions and venting rules most inspectors look for. Always check IPC/UPC versions adopted in your area.

• Toilet (water closet)

  • 12-inch rough-in from the finished wall to flange centerline (some toilets are 10 or 14 inches—verify model).
  • Minimum 15 inches from centerline to each side obstruction; 18 inches is more comfortable.
  • 21 inches minimum clearance in front; 24 inches preferred.

• Lavatory (bathroom sink)

  • Drain centerline: ~18 inches above finished floor.
  • Hot/cold stubs: ~21 inches above finished floor, set 4–6 inches left/right of centerline.
  • Stud depth: leave room for P-trap alignment; avoid notching supporting studs.

• Shower/tub

  • Shower drain: 2-inch minimum.
  • Shower valve: 38–48 inches above finished floor for showers; for tub/showers, valve often 28–36 inches above floor with spout 4–6 inches above tub rim. Check the trim kit’s spec.
  • Shower head: 78–80 inches above finished floor is typical.
  • Niche and bench heights: plan now; waterproof later.

• Venting basics

  • Every trap needs a vent. The vent must tie in above the trap weir and before the trap arm runs too far.
  • Typical maximum trap-arm distances (check your code):
    • 1-1/4-inch trap arm: up to ~2 feet 6 inches
    • 1-1/2-inch trap arm: up to ~3 feet 6 inches
    • 2-inch trap arm: up to ~5 feet
    • 3-inch trap arm: up to ~6 feet
  • Keep trap-arm slope gentle (about 1/4 inch per foot). Too steep can siphon the trap.

• Wet vent rules (high-level)

  • Wet venting can allow certain bathroom fixtures to share a vented drain.
  • Under most versions of UPC, a bathroom group on the same floor can be wet-vented using a 2-inch (or larger) vented drain serving the lavatory as the vent for the tub/shower and toilet downstream. The toilet must be 3-inch minimum. Details vary—ask your AHJ which code applies.
  • Under IPC, wet venting is more flexible but still requires sizing by DFUs and correct ordering of fixtures.
  • Do not install flat vents (horizontal vents below the flood rim).
  • No S-traps. Always use a P-trap with a vent.

Common mistakes that cause fails

• Flange set on the subfloor without accounting for tile thickness (toilet rocks or leaks).
• Vent tied in below the trap weir or vent laid flat too low.
• Long trap arms beyond allowed distances.
• Shower drain keepers set off-center to the tile layout.
• Using unapproved fittings (tight 90s) on horizontal drains instead of long-radius fittings.

Material Choices 🧰

Smart material choices save noise, callbacks, and future headaches.

• PEX vs. copper

  • PEX
    • Flexible, fewer fittings, fast to install.
    • Resists freeze damage better than rigid pipe.
    • Use listed crimp, clamp, or expansion systems per manufacturer.
    • Protect against UV and physical damage; add nail plates at studs.
  • Copper
    • Time-tested, rigid, and heat-resistant.
    • Soldered joints require careful prep and fire safety.
    • Can transmit more sound; may require isolation at hangers.

• Trap types

  • Use P-traps only. S-traps and drum traps are commonly prohibited.
  • Keep cleanout access available. Many codes require a cleanout on the trap arm or at the stack.

• Low-noise drain options

  • Cast-iron or foam-insulated pipe can quiet shower and tub drains.
  • Use isolation clips and avoid rigid pipe-to-wood contact to reduce structure-borne noise.

• Shutoff valves and access

  • Install quarter-turn stops on supplies to the toilet and lavatory.
  • For tub/shower valves, use valves with integral stops where allowed. Add an access panel behind the tub/shower valve if the manufacturer recommends service access.
  • Label shutoffs. Future you will thank you.

• Corrosion and compatibility

  • Use dielectric unions when transitioning from copper to steel.
  • Use no-hub couplings listed for the pipe materials you’re joining (e.g., shielded couplings for cast-iron to PVC/ABS).

• Backflow prevention

  • Handheld showers typically require vacuum breakers per ASME A112.18.1.
  • Check if your city requires backflow testing after certain fixture changes. H.I.S. Plumbing performs backflow testing and backflow prevention installations.

Waterproofing and Testing 💧

Tile is not waterproof. Your waterproofing and tests protect the structure, not the grout.

• Shower pan and flood tests

  • Build the pan with a code-approved liner or bonded waterproofing membrane.
  • Slope the pan base to the drain at 1/4 inch per foot.
  • Flood test for 24 hours before tile. Fill to below the threshold per your inspector (often to the top of the curb minus 1 inch). Mark the waterline and check for any drop.

• Walls and board

  • Use cement board, fiber-cement board, or foam backer boards in wet areas.
  • Regular “greenboard” drywall is not approved for shower walls in many codes.
  • If using sheet membranes or liquid-applied membranes, verify they meet ANSI A118.10. Follow manufacturer cure times before flood testing.

• Penetrations and sealants

  • Seal valve bodies, spouts, and accessory penetrations with gaskets or 100% silicone per the trim manufacturer.
  • Use appropriate sealant at tub flanges and the bottom of boards to decouple from pans.

• Pressure testing supply lines

  • Follow your adopted code (IPC/UPC). Typical requirements:
    • Water test at not less than working pressure (often 50–100 psi) for 15 minutes with no drop.
    • Some jurisdictions allow air testing at 50–80 psi (use caution; air is more hazardous).
  • Cap all stubs and plug all fixtures not yet installed.

• Drain/vent testing

  • Many AHJs require a 10-foot head water test or air test at 5 psi for the DWV system. Confirm which method your inspector wants.

Reference standards to know (by name)

• International Plumbing Code (IPC)
• Uniform Plumbing Code (UPC)
• International Residential Code (IRC)
• Tile Council of North America (TCNA) Handbook
• ANSI A118.10 (waterproofing membranes)
• ASSE 1016/ASME A112.1016/CSA B125.16 (pressure-balancing and thermostatic mixing valves)

Future-Proofing

Think about tomorrow while the walls are open.

• ADA-friendly heights and blocking

  • Add 2x8 or 2x10 blocking for future grab bars at 33–36 inches above the floor.
  • Consider toilets at 17–19 inches seat height (often called “comfort height”).
  • Mount vanity tops at 34 inches if you want wheelchair-friendly access.

• Anti-scald valves and tempering

  • Use listed pressure-balancing or thermostatic valves (ASSE 1016). Set max temperature with the factory limit stop.
  • Consider a thermostatic mixing valve at the water heater to deliver safe temps while allowing a higher tank setpoint.

• Smart leak detection and shutoffs

  • Install smart valves and sensors under sinks and near the toilet. Automatic shutoff can prevent major damage while you’re away.
  • Add hammer arrestors where quick-closing valves (like fill valves) can bang.

• Water quality and longevity

  • Whole-home filtration or point-of-use filters can protect finishes and valves.
  • If your home has galvanized or polybutylene, consider partial or full repiping now.

Problem/Scenario: The Week Before Tile 🛠️

You’ve demoed the bath, rough plumbing is in, and tile starts next week. But a friend’s project failed at inspection and they had to tear out fresh tile to fix vents. That’s the nightmare we want you to avoid.

Use this checklist as a pass-or-fix plan:

• Verify rough-in dimensions against your fixture cut sheets.
• Confirm vent distances and pipe sizes match your adopted code.
• Pressure-test supplies and flood-test the shower pan.
• Photograph everything with a tape measure in frame.
• Schedule your inspection before insulation and drywall.

H.I.S. Plumbing fields emergency plumbing calls from remodels that went sideways at this stage. A few hours now can save weeks later.

Quick Safety Checklist ✅

Before you solder, cut, or test:

• Turn off water at the main and verify with a faucet.
• If soldering, have a fire extinguisher, flame-resistant shields, and a water spray bottle ready. Protect studs and insulation.
• Use PPE: gloves, eye protection, hearing protection, and a mask when cutting cement board.
• Test for lead paint and asbestos before disturbing old walls or floors in older homes.
• Support heavy fixtures and tubs; never rely on a single screw or nail while test-fitting.
• If your bathroom is near gas appliances, keep flames and sparks controlled and ventilate the space.

Plan and Permit: A Step-by-Step Pre-Tile Checklist

• Map every centerline
  • Toilet, lav, tub/shower valves, head, spout, and niche. Mark finished-wall planes, not studs.
• Confirm framing upgrades
  • Add blocking for grab bars, vanities, shower doors, and accessories.
  • Frame curbs and benches with materials compatible with your waterproofing.
• Size and route
  • Choose pipe sizes based on DFUs and distance. Keep drain runs short and direct with long-sweep fittings.
• Vent strategy
  • Decide if you can wet-vent the bathroom group or need individual vents.
  • Plan vent rises vertical until 6 inches above the flood rim before offsetting.
• Permits and inspections
  • Submit fixture list and layout with your permit if required.
  • Request rough-in and flood-test inspections. Ask if photos are allowed for hidden work.

Local nuance: Code versions and interpretations differ. One city may allow AAVs; another may not. Inspection schedules can vary from next-day to next-week. Build that into your timeline.

Rough-In Essentials: Dimensions You Can Trust

Use manufacturer cut sheets as the final word. Typical standards help, but trim kits vary.

• Toilets

  • Flange top should sit flush with finished floor. If you set on subfloor, raise with spacers or wait for tile before final setting.
  • Leave room for the supply stop and a straight shot for the wax ring or seal.

• Lavatory and vanity

  • Leave 20–22 inches knee space if you’re targeting more accessible use.
  • Stubs should clear drawers and sink bowls. Dry-fit the vanity before soldering.

• Tubs and alcoves

  • Check tub ledger heights and level the rim. Out-of-level tubs create uneven grout joints and drainage issues.
  • Use brass or approved plastic waste-and-overflow kits. Test with a tub-fill before closing.

• Shower details

  • Verify valve depth with the plaster guard. Set it flush to finished wall per the trim spec.
  • Pre-slope under traditional liners. Bonded-membrane systems require different methods—follow the exact manufacturer sequence.

Venting: Avoid these common mistakes

• Venting downstream of a toilet on a horizontal drain (often not allowed in wet-vent setups).
• Using a tee on its back for horizontal-to-horizontal drainage. Use a wye and 45 or combo.
• Forgetting a vent for a standalone tub. That long trap arm is a siphon risk.

Material Choices: Quiet, Repairable, Code-Friendly

• Pipe and fitting brands

  • Stick with listed, code-accepted brands. Mixing off-brand fittings with name-brand pipe can cause leaks or failed crimp profiles.

• Valves and stops

  • Quarter-turn ball valves at mains and branches, not multi-turn gate valves.
  • Consider service stops on shower valves for faster repairs later.

• Sealants and thread treatments

  • Use PTFE tape and/or approved pipe dope on threaded connections; never on compression or flare joints.
  • Avoid over-tightening. Most leaks come from overtightened tapered threads.

• Noise control

  • Isolate supplies with cushion clamps.
  • Use cast-iron or foam-wrapped PVC/ABS for stacks next to bedrooms.

• Access panels

  • Place discreet panels behind tubs and stacked washer/dryer closets to reach traps, AAVs (if allowed), and valves.

Waterproofing and Testing: Pro-Level Steps

• TCNA-backed methods

  • Follow a TCNA method (e.g., B421, B422, etc.) that matches your system—traditional liner or direct-bonded membrane.
  • Don’t mix systems. A little bit of everything leads to leaks.

• Corners and seams

  • Preformed inside/outside corners reduce pinholes.
  • Embed mesh or use manufacturer banding at all seams.

• Curb and doorways

  • Ensure the top of the curb is at least 2 inches above the drain height.
  • Slope the curb top inward 1/16–1/8 inch per inch.

• Document the tests

  • Photograph gauges during pressure tests and the waterline during flood tests with timestamps. Inspectors and warranty teams value this proof.

If in doubt, ask your AHJ to confirm the test method by code section (e.g., IPC 312, UPC 406/609). H.I.S. Plumbing performs code-cited tests and provides documentation for your records.

DIY vs. Call a Pro

DIY-friendly

• Installing shutoffs and supply lines to a vanity.
• Setting a toilet on an existing, correctly placed flange.
• Swapping a faucet or shower trim when valve depth is right.
• Installing access panels and insulation.

Call a pro

• Moving a toilet or shower drain (affects venting, DFUs, and possibly structural members).
• Wet vent design and vent rework. Small mistakes here cause big problems later.
• Shower pan construction and flood testing—especially with linear drains.
• Repiping old galvanized, fixing low water pressure, or balancing hot/cold lines.
• Gas line work for combination boilers or relocated water heaters near the bath. H.I.S. Plumbing performs gas safety checks.

If you open a wall and find surprises—rotted subfloor, illegal S-traps, hidden tees on their backs—pause. Bringing in a licensed plumber can keep your permit and timeline on track.

What Pros Do On Arrival

When H.I.S. Plumbing arrives for a bathroom remodel rough-in, we:

• Confirm your city’s code version (IPC or UPC) and any local amendments.
• Review your fixture cut sheets and set exact heights and depths per the manufacturer (warranty-friendly documentation).
• Size drains and vents by DFUs and layout. Where allowed, we design efficient wet vents; where not, we individually vent fixtures.
• Pressure-test supplies and water-test or air-test DWV to code, then flood-test the pan.
• Photograph and label rough-in measurements on studs for your inspector and tile installer.
• Install shutoffs and plan access points for future maintenance.
• Provide notes on prevention: water hammer arrestors, PRV checks, and filtration options.

Our team is code-savvy and installs to manufacturer specifications. That combination helps you pass inspections and enjoy a leak-free bathroom.

Prevention & Maintenance

Little details prevent big problems:

• Pressure regulation
  • Keep house pressure around 60–75 psi. If it’s higher, discuss a pressure reducing valve (PRV).
• Water hammer
  • Hammer arrestors at quick-closing valves (toilet/lav) stop banging pipes.
• Easy access
  • Don’t bury cleanouts or AAVs (if permitted). Provide panels that blend with finishes.
• Backflow protection
  • Use vacuum breakers on handheld showers and hose bibbs. Schedule regular backflow testing if required by your city.
• Seasonal checks
  • Insulate pipes on exterior walls. In cold climates, avoid running supplies in unconditioned spaces.

Costs & Time Factors (Ranges, Not Quotes)

• Permits and inspections
  • Plumbing permit: varies by city; budget for application fees and re-inspection fees if needed.
• Materials
  • PEX or copper, valves, traps, and waterproofing systems vary widely by brand and method.
• Labor and timeline
  • Rough-in for a standard bathroom: 1–3 working days depending on scope and access.
  • Inspection lead time: next day to a week, depending on local workload.
  • Flood test: 24 hours minimum, plus inspector sign-off.
  • Unexpected repairs (rot, framing, repipe) add time. Build in contingency days.

Tip: Book inspections early and confirm whether your inspector wants the pan filled at the time of arrival.

When It’s an Emergency

Sometimes a remodel turns into an urgent call:

• You cut into a wall and find an active leak.
• The shower pan fails the flood test and water spots appear below.
• A valve won’t shut off and water won’t stop.

Shut the water at the main, open a lower faucet to relieve pressure, and call H.I.S. Plumbing for emergency plumbing service. If you’re searching “Emergency Plumbing near you,” we’re available 24/7 to stabilize leaks, cap lines, and keep your home safe so the remodel can continue.

FAQ

• Do I need a permit to remodel a bathroom?

  • If you’re moving plumbing or replacing valves inside the wall, most jurisdictions require a permit and inspections. Like-for-like fixture swaps on existing connections may not, but always ask your AHJ.

• How long should I flood test the shower?

  • Many inspectors require 24 hours. Some accept same-day tests if the water level is stable during the inspection. Confirm with your inspector.

• Can I use an air admittance valve (AAV) for venting?

  • Some cities allow them; others do not. Even where allowed, AAVs must remain accessible and sized correctly. Ask your building department before installing.

• What slope do I need on a bathroom drain?

  • Typically 1/4 inch per foot for 3-inch and smaller. For 4-inch and larger, some codes allow 1/8 inch per foot. Keep the slope even and the pipe supported.

• Should I insulate bathroom pipes?

  • Yes, insulate hot supplies for energy savings and comfort. Insulate cold lines in humid areas to reduce condensation, and protect any pipes near exterior walls from freezing.

Local/Seasonal Considerations

• Code versions and amendments

  • Cities adopt different editions of the IPC, UPC, and IRC. Local amendments can change vent distances, AAV acceptance, and test methods. Always check with your AHJ.

• Inspection timelines

  • High-demand seasons can stretch inspection schedules. Book ahead and plan flood tests to line up with inspector availability.

• Climate and construction type

  • In cold regions, avoid exterior-wall plumbing. In slab homes, moving drains may require concrete cutting and patching.
  • In seismic zones, verify bracing and strapping requirements, including for nearby water heaters that serve the bath.

• Water quality

  • Hard water shortens the life of cartridges and heaters. Consider filtration or conditioning while the system is accessible.

Your Pass-First-Time Checklist (Print This)

• Permits pulled; inspection windows scheduled.
• Fixture cut sheets on site; rough-in heights marked on studs.
• Drain sizes and slopes confirmed; long-sweep fittings used.
• Vent plan verified; trap-arm distances within code; no flat vents or S-traps.
• Toilet flange height set for finished floor thickness.
• Shower valve depth set with plaster guard flush to finish spec.
• Pan pre-sloped and flood-tested 24 hours; curb and corners sealed.
• Supply system pressure-tested with photos; DWV test documented.
• Shutoffs installed; access panels planned.
• Blocking installed for grab bars, doors, and accessories.
• PRV and water pressure checked; hammer arrestors added where needed.
• Photos of everything before insulation and wallboard.

H.I.S. Plumbing helps homeowners plan, rough, test, and document bathrooms to pass inspections and stay leak-free. From emergency plumbing stabilization to full bathroom plumbing, we install to code and to manufacturer specifications so your tile goes on once and stays there.

Authoritative references mentioned in this guide

• International Plumbing Code (IPC)
• Uniform Plumbing Code (UPC)
• International Residential Code (IRC)
• Tile Council of North America (TCNA) Handbook
• ANSI A118.10 for waterproofing membranes
• ASSE 1016/ASME A112.1016/CSA B125.16 for anti-scald valves
• CDC guidance on cross-connection and backflow prevention
• EPA WaterSense for efficient fixtures

Need help now or want a code-savvy walkthrough before tile? Our licensed team handles Emergency Plumbing, Drain Cleaning, Leak Detection, Pipe Repair, Fixture Installation, Backflow Testing, Sewer Line Repair, Water Heater Installation and Repair, and more.

Call H.I.S. Plumbing now — or reach us anytime at  1-888-778-7167 .