A Quick Primer on Rough In Plumbing

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.

Pipe layout for your bathroom rough in

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.

The waste-water system must be vented, to permit waste-water to flow smoothly and allow for the escape of methane gas. This requires the plumbing system to have a pipe that extends upward, though the roof, and vents outdoors. Each plumbing fixture is required to have its own trap, or a U-shaped pipe that will remain filled with water, to prevent sewer gas from entering the living space.

No matter how expertly a system is constructed, clogs are inevitable. As such, local plumbing codes will specify where cleanouts must be installed.

copper water supply pipes rough in

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.

The Fixtures

The only requirement for installing fixtures is making sure there is enough space for people to have access. For example, typically the center of a toilet should be mounted 15 inches from a wall or vanity on all sides.

roughing in plumbing

Steps for Roughing in your Plumbing:

    This guide will show you a quick and easy way to rough in your plumbing using 4 simple steps.

  • Step 1)Mark Key Locations
    Determine where all the toilets will be and mark its center on the wall and measure out 13 1/2 inches from that point. Make a mark on the floor at that point for the toilet flange. Center the actual flange on top of the mark and trace a line around the outside of the ring.
  • Step 2) Cut the Drain Hole
    Cut out the marked section and position the flange in the hole with the two elongated slots to the sides. Screw the flange to the floor, shimming as needed.
  • Step 3) Drain Pipe Installation
    Drain-pipe trap and vent assemblies must both be installed beneath the floor. Bear in mind that during roughing-in work that only subfloors are installed, so there are no problems placing drains under the floor. Direct the drain towards the main waste-water pipe, call the “waste stack,” with a 3-inch long, 90-degree turn fitting, running it into a 3-inch by 3-inch by 2-inch Y-shaped fitting. Position the Y fitting so the 2-inch opening can be connected to the main vent pipe.
  • Step 4) Supply Line Installation
    Run a supply line up through the floor or wall so it comes out nearest the side of the toilet-tank water supply fixture. Attach a “T” fitting to the top of the supply line so the water line going into the middle outlet of the T extends upwards. Attach an 8-inch piece of supply line onto the part of the “T” that will supply the toilet and attach a screw-on cap fitting to create an air space to prevent "water hammer."

Now that you have your plumbing roughed in, it is time to call the building inspector. If you have followed all the steps correctly you should receive approval to begin the finishing steps to complete your plumbing installation. Check out our selection of modern bathroom vanities to find some inspiration for your bathroom remodel.