Home Improvement Exterior Remodel Framework

What Is Rough-in Plumbing?

Find out what rough-in plumbing means and how to tackle this project

A home at the "rough in" stage

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Rough-in plumbing is the initial process of installing water supply lines, drain lines, vents, and pipeline connections after the foundation and framing are complete. Some rough-in plumbing is done before a slab is poured. Once this basic infrastructure is in place and approved by a building inspector, plumbing professionals can move to the finish plumbing phase. Find out more about rough-in plumbing, what it is, and why it's important to get it right.

What Is Rough-in Plumbing?

Rough-in plumbing is the process of installing vents, sewage systems, connections, and water supply lines. It can also refer to the stage of construction after the basic framing is complete and the initial services, such as electrical wiring or pipes, have been installed, but their end-points, like outlets or fixtures, have not been installed. This phase is completed before any walls are enclosed.

During the rough-in stage, the excavation and laying of underground pipes running from the utility connections to the main structure is completed. The pipes are then routed through wall cavities, the vents stacks are run to the roof, drain lines are connected to the sewer system or septic system, water lines are connected to the main water supply valve, and pipeline connections are made. When the rough-in phase is complete, the finish plumbing phase can begin.

Rough-in vs. Finish Plumbing

Rough-in plumbing is the initial stage of installing the plumbing infrastructure in a new home or addition before the walls are closed. Finish plumbing is the next step in the process when the plumber begins installing faucets, under-sink drain assemblies, water system valves, and other fixtures.

  • Rough-in plumbing is generally handled by a professional plumber who will excavate the yard to run underground water and drain lines from the utility connections to the main structure, and drill holes for water lines, drain lines, and vent stacks where appropriate throughout the home. After drilling the holes, the plumber runs water pipes, drain lines, and vent stacks through the wall cavities, making pipeline connections where necessary.
  • Finish plumbing follows after the completion of the rough-in plumbing stage either handled by an experienced DIYer or professional plumber. Caps on the drain and water supply lines are removed and plumbing fixtures are installed. The plumber sets up under-sink drain assemblies, installs water system valves, and tests any connections for leaks.

How to Do Rough-in Plumbing

DIY rough-in plumbing is not recommended unless you have professional experience and are up to date on building code and inspection requirements. However, you may be able to install a portion of the rough-in plumbing for a new bathroom, kitchen, or laundry room in an existing home depending on your skill. Rough-in work should be inspected before finish plumbing begins.

When you are tackling rough-in plumbing, consider these factors:

  • Gravity: Position drain lines so they angle downward; gravity is a key component of any drainage system.
  • Horizontal drains: Avoid long horizontal drain line runs as much as possible.
  • Venting: Ensure that the wastewater system is properly vented to avoid future issues with the home plumbing infrastructure.

How to Do Rough-In Plumbing

  1. Excavate and Lay Main Water and Drain Lines

    Excavate the area required to run water lines and drain lines from the utility connections to the main building, which is the first step.

    Complete the connections yourself if you have the experience, or hire a plumber to run the main water line and main drain line from the utility connections to the building.

  2. Measure and Drill Tub and Toilet Drains

    After installing the main water and main drain lines, focus on the bathrooms.

    Set and level each tub so you can mark where the drain will go, then remove the tub and drill the hole for the drain. Make sure that you are not positioned over a floor joist before drilling the hole. Reposition the tub and set it with 2-inch screws.

    Measure and mark the position for the toilet. In general, the toilet should sit about 13 inches off the back wall and a minimum of 15 inches from the tub. Use a hole saw to drill out the hole for the toilet drain.

  3. Drill Holes for Drainage and Venting

    Use a hole saw to drill holes to route drain lines and vent stacks through the wall cavities. Remember to factor in gravity when positioning drain lines so you don't inadvertently install long horizontal drain runs.

    When gluing drain fittings together, use the application brush to liberally coat the pipe and the inside of the fitting. Push the pipe into the connection, then rotate left and right to ensure there are no bare spots inside the glue joint. Wipe off any excess glue before it sets.

    Extend vent stacks from the basement through each floor of the home to the roof. Get into the attic to connect the appropriate vents and terminate them outside.

  4. Drill Holes and Run Water Lines

    Install the water lines now that the drain and vent lines are in place. Typically, it's a good idea to run 3/4-inch pipes as close to where they are required for the bathroom, kitchen, or any water-using appliances, like the fridge, washing machine, or dishwasher. Then reduce the 3/4-inch water line to a 1/2-inch line for each fixture.

    Make the length of a 1/2-inch pipe as short and straight as possible. Take the opportunity to drill holes in the exterior of your home for any hose bibs. Depending on your geographic location, it may be beneficial to angle the hose bib lines upwards to help prevent freezing during the winter months.

  5. Externally Vent Plumbing Equipment

    Drill vent holes for any additional plumbing equipment, including sump pumps, water heaters, and boilers. Double-check the blueprints to determine where the plumbing equipment will be installed in the home, then drill out the holes for external venting.

  6. Complete Water, Drain, and Vent Tie-Ins

    Run the primary hot and cold water lines in the basement, drop the main 3-inch drain stack, and run the central vent stack.

    Connect cold and hot water lines to the primary water lines, then tie in the various drain lines to the main 3-inch drain stack.

    Connect the vent lines to the central vent stack and tie together the drain lines for any half baths.

    Ensure the hot and cold water lines run to where the water heater will be installed.

  7. Connect and Test the Water Line

    Connect the water lines to the main incoming service and install a main shut-off valve.

    Cap or install the isolation valve on any water lines that are currently open, then turn on the water to test the plumbing system for leaks.

    Rough-in plumbing is just the start of the installation process, so if you spot any issues, fix the problem now before hanging drywall which will cover up the plumbing infrastructure.

FAQ
  • What is rough-in plumbing and how is it done?

    Rough-in plumbing is the stage when the plumber excavates and lays water and drain lines from the utility connections to the building. They will then route the water lines, drain lines, and vent stacks through wall cavities in the home. Water lines are then connected to the main water supply valve, drain lines are connected to the sewer or septic system, and vent stacks run to the roof.

  • What does rough-in plumbing mean and is it difficult?

    Rough-in plumbing is essentially putting in the entire plumbing infrastructure for the home. It's a complex process that takes time and experience to complete without issues. The best way to complete rough-in plumbing for your new home is to hire a professional plumber. It isn't recommended to tackle rough-in plumbing work as a DIY project.

  • What is the stage before rough-in plumbing?

    Mapping out the main drain location, laying the foundation, and framing the house are the stages before most of the rough-in plumbing can be done.

  • How long does it usually take to do rough-in plumbing?

    On average, an experienced professional plumbing crew can complete rough-in plumbing within a few days but on an actual job site, there may be delays that can increase the timeline to a few weeks. If you are concerned about the length of time, speak to your plumber to get an estimate and work with them to help facilitate the rough-in installation.