How to Add New Plumbing Upstairs for a Bathroom

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Adding plumbing involves running supply and drain lines.
Image Credit: AndreyPopov/iStock/GettyImages

Add value and convenience to any home by installing a new bathroom on an upper floor. Setting the plumbing for a new bathroom requires you to connect water supply pipes and drainpipes to existing systems. Once the new bathroom plumbing is in place, you can add fixtures and furniture to complete the room.

Access Existing Plumbing Lines

Step 1: Get a Permit If Needed

Contact your local building department to see whether a permit is needed for adding new plumbing.

Step 2: Cut Drywall to Access Lines

Remove the drywall in the bathroom against a wall that has the nearest access to the plumbing lines, if there is no direct access to plumbing within an access panel in the room. The drywall can be removed using a reciprocating saw and a drywall blade. Pull out the drywall in small sections and discard.

Step 3: Turn Off Water Supply

Turn the main water line ball valve 90 degrees clockwise to shut off the flow of water to the entire plumbing system. Open all the faucet taps inside the house to drain as much water as possible from the lines.

Add Y-Coupler to Drain Line

Step 1: Find the Drain Line

Locate a drain line within the wall.

Step 2: Cut Existing Drain/Waste Line

Cut out a 5-inch section of the waste line using a hacksaw or pipe-cutting tool.

Step 3: Apply Adhesive to New Fitting

Apply a layer of ABS cement to the inside an ABS wye fitting.

Step 4: Install New Fitting

Press the fitting into the hole that you cut into the drain line until the fitting slips over both ends of the pipe. Make sure the opening on the wye fitting is pointed toward the inside of the bathroom to allow for easy access later on. Allow the cement to set for 10 minutes. Once dry, the wye fitting will provide a spot to connect the sink and toilet drains.

Prepare to Connect Supply Lines

Step 1: Locate Existing Supply Lines

Locate existing hot and cold water lines inside the basement, crawlspace or access panel, whichever is closest to the new bathroom.

Step 2: Measure a 5-Inch Section

Mark a 5-inch section on both the existing hot and cold water lines at the access point closest to the new bathroom.

Step 3: Cut and Clean Supply Lines

Cut on the marks with a pipe-cutting tool or hacksaw. Clean the edges of the cut pipes with a cloth to remove any plastic or copper shavings.

Connect the Supply Lines

Step 1: Add T-Fittings to Supply Lines

Place push-to-fit T-fittings into one side of each of the supply lines, with the third opening facing the direction of the bathroom. The fitting will audibly snap into place.

Step 2: Connect Other Side of T-Fitting

Gently pull back on the fittings and the other side of the cut pipe to slip the pipes into the other side of the fittings. Release the fitting and the pipe to complete the connection.

Step 3: Add New Water Lines

Thread the new water pipes into the wall in the direction of the bathroom and insert the base of the pipes into the openings on the T-fittings. This will connect the water lines to the existing plumbing system.

Step 4: Push Supply Pipes Through Wall

Have a helper guide the tops of the pipes into the opening in the upstairs bathroom wall. Temporarily secure the tops of the pipes against a stud in the wall by placing a pipe strap around each line and tapping the provided nails into the studs. This will hold the lines in place until you are ready to add furniture and individual fixtures.

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Heath Robert

Heath Robert has been a professional writer since 2001. Covering news, politics and local communities, he has worked for daily newspapers across Colorado, including the "Columbine Courier" and the "Colorado Statesman." Robert holds Bachelor of Arts degrees in journalism and political science.