Rough-in Plumbing in new Construction

Types of Rough-In

For inspection purposes, each type of machine has its own definition of the rough-in:

  • Electrical: A rough-in here means that all electrical cables have been pulled through studs and other framing members and are inserted into wall and ceiling boxes. But the light switches, outlets, lights, and other devices are not be attached-inspection of that aspect of the work occurs during the final inspection.
  • Plumbing: The rough-in here means that all water supply and drain pipes have been run through bored holes in the studs and other framing members, and that all pipe connections have been made. But no sinks, faucets, or other fixtures or end elements are yet installed at this phase.

Plumbing Meaning

Plumbing shall be defined as:

(a) Where there is a metering device inside the building or structure to which the water is being delivered for use, “plumbing” shall begin at the outlet or house side of the metering device which is closest to the inside face of the outermost foundation wall of that building or structure; and

(b) Where there is no metering device inside the building or structure to which the water is being delivered for use, “plumbing” shall begin at the outlet or “house” side of the main control valve which is closest to the inside face of the outermost foundation wall of that building or structure.

Plumbing Rough-In

Plumbers work with three basic categories of supplies. There are the supply pipes, that deliver the clean water into the house and to the plumbing fixtures, such as the sinks, toilets, and washing machine.

Rough in plumbing is, as its name suggests, basically a “rough draft” of your plumbing installation. The point is to get a diagram of your plumbing skeleton in place, a static and unchanging framework upon which you’ll complete your plumbing installation. This is beneficial because, once your rough in is approved, you can move forward with your construction or remodel or plumbing appliance installation without having real plumbing pipes getting in the way or posing an obstacle, but you’ll still know exactly where those pipes will be going once the project is ready for them.

Some municipalities allow homeowners to install their own plumbing systems, however, you may need to supply the building department with a rough-in plumbing diagram. The drawing doesn’t need to be fancy, but should just show what size pipes you plan to use and how the plumbing will be laid out and connected. The diagram is intended to show the plumbing inspector your proposed system will meet all the local code requirements, but it can also save you a lot of headaches, and expense. Once your diagram is approved, you are ready to begin laying the pipe.

Below are generally accepted plumbing rough-in measurements for sinks, toilets, and tub/showers. If you find the numbers alone cryptic, reference the details below the table. Also, see Notes at the very bottom for an explanation of the term “centerline.”


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Laying Out the Pipes

The waste-water system is usually installed first in the typical plumbing installation. This is because it is always easier to work smaller pipes around larger ones, than the other way around. The waste-water system is not pressurized, depending on gravity to function. This means all waste-water pipes must be angled downward, towards the septic outlet and away from plumbing drains, at a standard drop of at least 1/4 inches per each horizontal foot of pipe.

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Supply Line – Vertical8 1/4″2″ to 3″ higher than drain pipe80″ shower; 18″ tub
Supply Line – Horizontal6″ max from center4″ to left and right of center8″ apart
Discharge/Drain Hole From Back Wall12 1/2″N/A14″
Discharge/Drain Hole – Vertical0″16″ to 20″0″
Fixture – Side To Side Buffer15″ to 18″ min15″ to 20″ min18″ min
Fixture – Front Buffer21″ min21″ min18″ min


Recognizing the different types of pipes within your house is vital to knowing the right repair technique. The most common pipes used today are copper, PVC, or ABS. But, when dealing with older homes, you might encounter some other piping material. For example, homes built before 1960 used galvanized steel or cast iron DWV (drain/waste/vent) pipe systems.

Here’s a quick look at types of pipes commonly used in homes, beginning with the pipes used for DWV systems.



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  • Cast iron: Commonly used before 1960 for the vertical drain, vent stacks, and sometimes the horizontal drain lines. Cast iron is durable, but can rust over time. Call a professional plumber to replace rusted sections with plastic (PVC or ABS) and the correct transition fittings.

  • Plastic: Plastic pipe comes as either ABS (acrylonitrile-butadiene-styrene) or PVC (polyvinyl-chloride). Most homes since mid-1970 have plastic pipes and fittings because it’s inexpensive and easy to use. Simply glue the joints using a primer and liquid cement.

  • PVC: This white or cream-colored pipe is the most used pipe for drain lines. It’s strong, untouchable by chemicals, and seems to last forever! The rating and diameter is stamped right on the pipe.

  • ABS: This black pipe was the first plastic pipe to be used in residential plumbing. Today, many areas don’t allow ABS in new construction because joints can come loose. Check with your local plumbing inspector if you want to use ABS.

  • PEX: PEX (cross-linked polyethylene) is the newest pipe for residential use. Approved in many regions of the country, PEX is easy to install because it cuts easily, is flexible, and uses compression fittings. But, more permanent connections need a special crimping tool. PEX is three to four times more expensive than copper or plastic.

  • Steel: Galvanized steel pipe is common in older homes. Galvanized pipe is strong, but lasts only about 50 years. Before repairing, consider replacing instead. Call a professional to deal with it.
  • Copper: Copper pipe is resists corrosion, so it’s commonly used pipe in water supply lines. It costs more than plastic but it lasts! There are two common types of copper pipe:
    • Flexible copper, which is often used for dishwashers, refrigerator ice makers, and other appliances that need a water supply. It’s easy to bend, but if it kinks, you must cut the piece off and replace it. Sections of flexible copper pipe are joined using either soldered or compression fittings.
    • Rigid copper, which comes in three thicknesses. Type M is the thinnest but is strong enough for most homes. Types L and Type K are thicker and used in outdoor and drain applications. To cut rigid copper, you’ll need a wheel cutter, tube cutter, or a hacksaw.

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The Bathroom Takes Priority

Setting the tubs comes next. At first, you’ll need to physically set and level each tub and mark where the drain to the waste portion goes. Once you do this enough times, you’ll get to know your measurements by heart and be able to place cut the hole needed without placing the tub first. The best tool for creating the hole is a high-torque drill, like a Hole Hawg or Stud & Joist Drill.

Toilet Rough-In Details

  • Supply Line – Height: Ideally, 8 1/4″ above the floor. This cold-water-only pipe will create one hole between 5-10″ above the floor.
  • Supply Line – Horizontal: Imagine a centerline running vertically through the center of the toilet. The supply line hole should be 6 inches to the side of this centerline. Check your toilet to see which side the water supply intake will be, though it probably will be on the left side.
  • Discharge Hole From Back Wall: Off-set this hole from the back wall by 12 1/2″.
  • Discharge Hole – Vertical: Since this is located at floor height, the distance is zero.
  • Fixture – Side to Side Buffer: Measuring from the center point of the toilet outward, the bare minimum from side-to-side for a toilet is 15 inches to any wall or other fixture. It is recommended, though, that you increase that distance to 18 inches for more comfort if your bathroom layout allows.
  • Fixture – Front Buffer: From the front rim of the toilet, leave a space of at least 21″ to the nearest obstruction. The recommended buffer is 30″.
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Sink Rough-In Details

  • Supply Line – Height: Two holes. Vertically, both holes are about 2-3 inches above the drain pipe.
  • Supply Lines – Horizontal: One hole is 4 inches to the right of centerline, another hole is 4 inches to the left of centerline
  • Discharge Hole From Back Wall: N/A
  • Discharge Hole – Vertical: About 16-20 inches above the floor. We will consider the drain pipe to be a vertical centerline.
  • Fixture – Side to Side Buffer: From centerline, 15″ minimum, 20″ recommended
  • Fixture – Front Buffer: Minimum distance to nearest obstruction is 21″. Recommended is 30″.
  • Placement of Sink: Vertically, the sink should be about 31 inches above the floor. Measure up to the rim of the sink.

Shower and Bathtub Rough-In Details

  • Shower Supply – Vertical: 80″. This is the highest point, the place where the shower nozzle will go.
  • Tub Supply – Vertical: Stubs 18″ high. 10″ above tub spout. Place one faucet 4″ to the left of centerline and the other faucet 4″ to the right of centerline.
  • Discharge Hole From Back Wall: Place drain on the centerline. Total opening for drain access can be between 10″-14″ off-set from framing, and 6″-8″ wide.
  • Discharge Hole – Vertical: Since this is located at floor height, the distance is zero.
  • Fixture – Side to Side Buffer: 18″ minimum required buffer.
  • Fixture – Front Buffer: 18″ minimum required buffer.

Further Notes

  • Centerline: When we speak of dimensions, the word “centerline” is used. As with the term “on-center,” which is used for construction, the term “centerline” is an imaginary vertical line drawn through a key reference point (usually the drain pipe). So, if two pipes are ten inches apart, we measure from the center points of each pipe, not the edges.
  • Base Floor Height: Also base floor height is considered to be the subfloor (in new construction) or finish floor (in remodeling). Not all of these dimensions are set in stone. Consider them general guidelines. They will vary according to your bathroom. Consult the instructions that come with the fixture (sink, tub, etc.) for more precise dimensions.

Drains and Vents

Now it’s time to drill out the holes for drainage and venting. If you weren’t already using a Hole Hawg style drill, you will really want one at this stage. Usually what I do upstairs is pop all my vents up into the ceiling.

One very important thing in the plumbing trades are the following words: drainage MUST grade. For everything up to 3” pipe, the grade must be set to ¼” per foot and 4″ pipe must be set to 1/8“ per foot.

Making the Connection

When gluing fittings together in a new build, there is no such thing as too much glue. With your application brush, coat the pipe as well as the hub of your fitting with a generous serving of glue, then when it comes time to put your fitting on and grade it, push on and rotate left then right before setting your grade. The reason we do this is to ensure that there are no bare spots inside the glue joint. Then once the fitting is in place, wipe off the excess glue.

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Plumbing Diagram

Plumbing Diagram

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Water Supply Pipes

The main cold-water pipe supplies water to the individual lines that supply water to the fixtures throughout the house. Supply pipes are typically copper or PVC, with copper being more durable and expensive. Copper pipe joints can be soldered or flare-fitted, whereas PVC joints are cemented.

Plumbing Diagram

Plumbing Diagram

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Water Lines and More Hole Drilling

Now that we’re done with the drainage and venting into the basement, what next? If you have an apprentice, you will probably let him or her focus on running water lines to the upstairs for the fixtures.



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All Tied Up At the Moment

Plumbing Rough In Once you get into the basement, it’s time to start with tie-in’s. This usually consists of tying the half bath together, running the emergency floor drain for an upstairs laundry into the mechanical room and stubbing it down a ways to ensure it doesn’t get covered over later on in the build, and preparing the vent for your rough-in double plumbing (a fancy way of saying your basement bathroom vent). Additionally, you’ll need to drop your main 3″ stack along with a possibility of another 3″ stack depending how on you were forced to run the drainage to the upstairs.

Kitchen Specifics

The tie in type you use for kitchen sinks will depend on the sink placement. If the sink is going in an island that you can completely walk around, then you can simply angle the drain up with a 45° fitting and stud it through the floor roughly eight inches. The reason you don’t have to do anything else here is that you’ll use an air admittance valve (aka cheater vent).

Tying Up Loose Ends

Tie-ins also involve running the water lines in the basement. Do this and you’re almost home free! Just run your 3/4″ PEX to the mechanical room, adding headers along the way for any main floor or basement fixtures that have been roughed in and terminate the hot and cold lines around where the hot water tank is going.


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Backwater Valves

The next step here in Alberta is to install a device called a normally open backwater valve. What it does is protect the house should the sewers back up for any reason. If this happens, a flap comes up and seals the house off from any potential dangers.

Backwater valves typically come in two styles – normally open and normally closed. The normally closed backwater valves can be used on branch drains that require protection for the fixture it is serving (i.e.: a basement laundry that needs to be tied in before the main backwater valve is installed). The reason we normally use an open backwater valve is that houses are used to vent the city plumbing system and need a constant flow of fresh air to keep things working properly.

Completing the Job

Once the groundwork is complete, the last step is to run your water service to where the prints call for it and install your water shut off. Then you can water test the house to ensure there are no leaks before drywall starts going up.

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