What Is Rough-in Plumbing?

Rough-in plumbing refers to the initial stages of installing the water supply and drainage systems in a building. This involves putting in place the pipes, fittings, and plumbing fixtures that will eventually connect to water supply lines and drain lines. Rough-in work is done before walls, floors, and cabinets are installed.

Why Rough-In Plumbing is Important

Rough-in plumbing is a crucial first step in any construction project. Getting the rough-in plumbing right sets the stage for an efficient system down the road. Here are some key reasons proper rough-in plumbing matters:

Allows Connections to Utilities

The rough-in plumbing includes installing drain, waste, and vent (DWV) pipes and water supply pipes. These pipes need to be strategically located so they can later connect properly to municipal sewer and water lines. Careful planning of the rough-in allows the system to hook up to these utilities.

Supports Fixture Installation

The drain, supply, and vent pipes installed during rough-in provide connection points for sinks, toilets, tubs, appliances, and other plumbing fixtures. The rough-in piping determines the optimal location for these fixtures.

Facilitates Testing

Once the rough-in plumbing is complete, pressure tests can be conducted. This involves sealing pipes and using water pressure or air pressure to check for leaks. Early leak detection makes repairs easier and prevents issues down the road.

Allows Inspections

Local building codes often require that plumbing work be inspected at various stages. Rough-in inspections happen before the pipes are enclosed in walls and floors. Inspectors check that piping is properly sized and located, and that the system meets code.

Minimizes Re-work

If plumbing issues are caught later in construction, significant demolition and repair work may be required. Proper planning and execution of the rough-in plumbing reduces the need for costly re-work later.

Elements of a Rough-In Plumbing System

A complete rough-in plumbing system includes the following components:

Drain, Waste, and Vent (DWV) Pipes

DWV pipes carry wastewater and sewage out of the building to the municipal sewer line or septic tank. This includes pipes for fixtures like sinks, toilets, tubs, and floor drains. Vent pipes allow air into the system to facilitate proper drainage and prevent trap seal loss.

Water Supply Pipes

Supply pipes bring fresh water into the building from the main water line. Hot and cold water lines feed different plumbing fixtures. Supply valves control water flow to specific fixtures or zones.

Pipe Fittings

Fittings like elbows, tees, couplings, and reducers join and transition pipes. Traps provide a water barrier to prevent sewer gases from entering the building. Hangers and brackets securely anchor and support pipes.

Drain and Vent Locations

Drain and vent pipe sizes and locations are determined based on the proposed fixture layout. Drain pipes usually run vertically through walls and horizontally through floors and ceilings.

Water Supply Manifold

A main water supply manifold acts as the central distribution point to feed the hot and cold supply lines running to fixtures. The manifold includes a main shutoff valve.

Pipe Insulation

Insulating supply pipes helps maintain water temperature. Drain pipes may be insulated to prevent condensation and noise.

Rough-In Plumbing Process and Planning

Careful planning and sequencing is crucial for an effective rough-in plumbing installation. Here is an overview of the process:

Review Building Plans

The plumber studies the building plans to understand the layout, location of fixtures, and any relevant details that impact the plumbing plan.

Create Plumbing Plan

A detailed plumbing plan is developed showing the routing, sizing, and materials for all supply and drainage piping. This accounts for code requirements, utility connections, and other factors.

Measure and Mark Locations

Once walls and floors are in place, the plumber measures and marks where pipes will be run and fixtures located. This is based on the plumbing plan.

Install Drainage Piping

DWV piping is installed first since it must be sloped properly for drainage. Pipes are run through studs and joists to the main stack and building drain connection.

Install Water Supply Piping

Hot and cold supply pipes are run from the planned manifold location to where fixtures will go. Pipe insulation may be added as the pipes are installed.

Install Valves, Fittings and Supports

Necessary valves, fittings, hangers, and brackets are added to complete and support the supply and drainage system.

Conduct Tests

The piping system is tested for leaks and proper functionality before inspection and enclosing in finished walls.

Arrange Inspection

The local building authority inspects the rough-in plumbing to ensure it meets code requirements before finishing work proceeds.

Common Rough-In Plumbing Materials

Plumbers select the best pipe materials for each application based on code requirements, performance needs, and costs. Common options include:

Plastic Piping – PVC, CPVC, PP, PE-X

Plastic pipe types like PVC, CPVC, PP, and PE-X are used for both supply and DWV systems. They provide a lightweight, durable, and cost-effective option.

Copper Tubing – Type L, Type M

Copper is also a popular choice, especially for water supply lines. Type L and Type M are the most common tubing types. ProPER fluxing and soldering method is crucial for copper.

Cast Iron Pipe

Cast iron is the traditional material for drainage systems. It is durable but heavy and difficult to cut and join. Newer plastics have displaced much cast iron rough-in work.

Galvanized Steel Pipe

Galvanized steel once saw wide use but has largely been replaced by longer-lasting plastic pipes. It is still used in some cases for vents and supplies.

Key Differences From Finish Plumbing

Rough-in plumbing varies from finishing plumbing work in some important ways:

  • Rough-in installs the supply and drainage system infrastructure. Finish work makes the final connections to fixtures.
  • Rough-in happens before walls/floors are finished. Finish work is done after surfaces are completed.
  • Rough-in only requires access to piping routes. Finish work needs full access to fixture locations.
  • Rough-in prioritizes proper slope and alignment of piping. Finish work focuses on secure fixture installation.
  • Rough-in accommodates finish components like valves and connections. Finish work directly interfaces fixtures with rough-ins.
  • Rough-in undergoes pressure testing and code inspection. Finish undergoes visual inspection and user testing.
  • Rough-in emphasizes proper system design. Finish emphasizes aesthetics and functionality.

Both stages require skill, planning, and attention to detail performed by qualified professionals.

Why Hire a Professional for Rough-In Plumbing?

While some very experienced DIYers can potentially perform their own rough-in plumbing, hiring a professional plumber is highly recommended. Here’s why:

  • Familiar with Codes – Pro plumbers understand the intricacies of the local plumbing code and ensure the rough-in meets all requirements.
  • Correct Sizing & Layout – They have the expertise to properly size and route pipes based on building plans and intended usage.
  • Precision Installation – Professionals have the skills to neatly and securely install rough-in components.
  • Know System Optimization – They know tricks and techniques to optimize system performance and prevent issues down the road.
  • Access to Equipment & Materials – Plumbers have the necessary tools, equipment and relationships with material suppliers.
  • Experience & Training – They have years of focused education and on-the-job training specific to plumbing.
  • Identify Unforeseen Issues – Pros can spot potential problems and adapt plans based on field conditions.
  • Arrange Inspections – They work directly with the building authority to coordinate rough-in inspections.

While always an option, taking on rough-in plumbing as a DIY project introduces significant challenges and risks.

What Gets Installed During Rough-In Plumbing?

The rough-in stage of plumbing involves installing all of the “inside” portions of the supply and drainage systems before the walls, floors, and fixtures are in place. This includes:

Drain, Waste, and Vent (DWV) Piping

  • Main drainage stack – Primary vertical DWV pipe receiving flows from branch fixture drains. Often 4-6″ diameter.
  • Main horizontal branch drains – Larger pipes joining other drains to the stack. Flow by gravity downhill.
  • Fixture drain lines – Smaller vertical and horizontal pipes tying into fixtures with p-traps.
  • Vent pipes – Vertical and horizontal pipes allowing air into the system for proper drainage.

Water Supply Piping

  • Hot and cold supply mains – 3/4″ to 1″ pipes bringing water from the main valve manifold.
  • Fixture supply branches – 1/2″ or 3/8″ pipes splitting off mains to feed individual fixtures.
  • Supply stops – Shutoff valves installed near fixture locations to allow isolation.
  • PEX manifold – Central distribution unit joining supply mains to fixture branches.

Fittings & Connections

  • Pipe fittings – Elbows, tees, couplings, unions, and transitions join and seal pipes.
  • Hangers & straps – Secure pipes to studs or structure and support proper slope.
  • Pipe insulation – Insulate hot water pipes and some drains/vents.
  • Pipe primer & cement – Bond pipes and fittings on PVC, CPVC systems.
  • Soldering – Join copper pipes and fittings using proper flux and solder.

Locations and Access Points

  • Pipe routes – Marked paths for piping through walls, floors, and ceilings per plan.
  • Stud/joist notching – Openings cut through framing members for pipes to pass.
  • Access panels – Removable panels allowing access to valves or critical points.

Testing & Inspection Prep

  • Pipe caps & plugs – Seal pipes for pressure testing. Removed later at fixture connections.
  • Temporary valves – Used to isolate sections for pressure testing, then removed.
  • Pipe identification – Labeling or tagging helps the inspector identify and assess piping.

Common Rough-In Plumbing Mistakes to Avoid

While a basic rough-in plumbing system may seem straightforward, there are some key pitfalls to avoid:

Improper Planning & Layout

  • Not carefully reviewing plans and coordinating with other trades
  • Incorrect pipe sizing and routing

Flawed DWV Installation

  • Drain slopes less than 1/4″ per foot grade
  • Undersized vent pipes
  • Too many bends that hinder drainage

Supply System Issues

  • Hot and cold lines reversed
  • Excessive pipe length from manifold causing lag
  • Supply stops missing or at wrong spacing

Pipe Joining & Support Errors

  • Leaky joints from improper solvent welding or soldering
  • Pipe shaking, sagging or stress due to inadequate supports

Access & Testing Problems

  • Failed to create needed access panels at critical points
  • Caps left off for inspection allowing debris into pipes
  • Closed valves inhibiting proper pressure testing

Code Violations

  • Notching studs excessively against code
  • Unapproved pipe materials used for hot water
  • Improper use of unions on drain or vent piping

Being attentive, meticulous, and thorough at the rough-in stage prevents many headaches down the road.

Typical Rough-In Plumbing Code Requirements

While specific plumbing code requirements vary between jurisdictions, there are some general standards that typically apply to rough-in plumbing work:

Drain, Waste & Vent (DWV) Piping

  • Minimum 1/4″ per foot slope on horizontal fixture drain lines
  • 2″ diameter vents for typical residential bathroom groups
  • Stud wall notching limitations – typically 40% of width
  • Approved materials like PVC, ABS, copper, or cast iron

Water Supply Piping

  • Minimum 3/4″ supply lines to fixtures
  • 1/2″ ball valve shutoffs within 36″ of fixtures
  • Approved piping materials like copper, CPVC, PE-X or PB
  • Maximum hot water pipe run lengths as per code table
  • Expansion loops on hot water lines as needed

Pipe Installation and Support

  • Horizontal drainage piping supported every 4 ft or less
  • Vertical piping supported at base and at each floor level
  • Hanger straps within 12″ of pipe joints
  • Pipes penetrating studs or joists within 1-1/4″ of framing

Testing & Inspection

  • Water pressure test minimum 50 PSI air or water for 15 minutes
  • Allowable pressure drop of not more than 5 PSI during test
  • Inspection of piping layout, sizing, slope, joints, valves, and supports

Fixture Locations

  • 30″ minimum clear space in front of toilets and lavatories
  • Shower controls located away from shower head per code
  • Mirrors not to obstruct light or medicine cabinets

Always check with local inspectors about specific rough-in requirements in your jurisdiction. Failing to follow code can mean ripping out and re-doing plumbing work.

Step-by-Step Rough-In Plumbing Process

Installing quality rough-in plumbing requires careful planning, measurement, execution, and testing. Here is an overview of the typical end-to-end rough-in process:

Design & Planning

  • Review architectural plans and visit site
  • Create detailed plumbing plan with pipe sizing and routing
  • Submit plan to inspector and request rough-in inspection

Prep Work

  • Deliver pipes, fittings, valves and other materials onsite
  • Confirm water/sewer line access locations with utilities
  • Verify framing meets clearance needs for planned pipe runs

Drainage Piping

  • Measure and mark drain line locations on floors/walls per plans
  • Select appropriate pipe sizes and layout with proper slope
  • Cut pipe lengths and test fit prior to joining
  • Glue fittings and pipes using proper primer and cement
  • Add hangers to properly support horizontal piping

Water Supply Piping

  • Measure and mark water supply routes from manifold to fixtures
  • Cut and test fit supply pipes based on measurements
  • Join copper tubing by soldering joints using acid flux
  • Solvent weld PEX, CPVC or PVC pipe fittings as applicable
  • Label pipes indicating hot and cold supply lines

Install Valves, Controls & Access

  • Install supply stop valves near planned fixture locations
  • Add water control valves like pressure reducing, tempering, backflow preventers
  • Create access panels where needed to reach valves or controls

Testing & Inspection

  • Seal pipe ends with caps and test systems under pressure
  • Repair any leaks found under pressure
  • Have inspector review installation for code compliance
  • Make any corrections required to pass inspection


  • Flush pipes to clear debris before making fixture connections
  • Add insulation on hot water pipes as needed
  • Seal openings and remove caps when ready for finish plumbing

Proper planning, meticulous installation, testing, and inspection leads to problem-free rough-in plumbing.

How Much Does Rough-In Plumbing Cost?

Rough-in plumbing costs depend on several factors, including:

  • Scope of work – Size of dwelling and number of bathrooms/fixtures
  • Local labor rates – Hourly plumbing costs vary by region
  • Material costs – Piping, fittings, valves and components selected
  • Permit fees – Costs levied by local building department
  • Site conditions – Ease or difficulty of access for installation

Typical Range of Costs

  • Small bathroom rough-in: $1,000 – $1,500
  • Standard 3 bedroom, 2.5 bath home: $4,000 – $6,000
  • Large custom home over 5,000 sq ft: $10,000 – $15,000+

Here are some of the key variables that influence rough-in plumbing costs:


Most rough-in plumbing costs go towards the professional labor time required.Complex layouts or difficult access can increase hours.

Drainage Piping

Type and length of drain pipes needed influences material costs. More fixtures and longer pipe runs add cost.

Supply Piping

As with drains, the amount and type of supply piping impacts budgets. More extensive systems and copper pipes add expense.

Valves & Fittings

Basic rough-in requires standard fittings and valves, but special applications add costs quickly.

Permit Fees

Some municipalities charge permit fees based on number of fixtures or drainage fixture units. More complex plans may also increase permit costs.

Site Factors

Access issues due to tight spaces or multi-story construction can drive up rough-in labor considerably. Previous demolition work may also add time and cost.

Overall, the more extensive the plumbing plan and the larger the dwelling size, the more the rough-in plumbing work will require in both labor and materials.

Saving on Rough-In Plumbing Costs

While proper rough-in plumbing is crucial, there are ways to control costs on basic projects:

Match Pipe Size to Need

Avoid oversizing pipes beyond code minimums. Only use larger pipes where truly needed.

Evaluate Pipe Material Options

Compare the cost of PEX, PVC, CPVC, and copper in your area. Use the least expensive code-approved option.

Install Drains Before Water Lines

Drainage piping takes more time. Doing this work first improves efficiency.

Perform Prep Work Yourself

Basic material delivery, site clearing, and prep work saves plumber hourly costs.