How to Install Rough-in Plumbing for a Bathroom

plumber wearing a tool belt and holding a large wrench
What You'll Need
PVC drainpipes
Toilet flange
Copper supply pipes
3-inch galvanized screws
PVC glue
Pipe cutter

<< How to Install Rough-in Plumbing for a Bathroom, Part 2

In the first and second part of this series of rough-in plumbing for your restroom renovation, you learned how to plan the project and begin installing fixtures for the tub and shower. Now, in “How to Install Rough-In Plumbing for a Bathroom, Part 3,” you can follow the directions below to begin installing the plumbing for your toilet and sink. Since the plumbing should mostly be done, in the form of supply lines and water pipes, installing the toilet and sink is easy.

Step 1 - Secure the Toilet Flange

With the rough plumbing already positioned, measure out 12 inches from the wall to the center of the drain hole for the toilet. Then, secure the toilet flange to the subfloor of the bathroom with three-inch galvanized screws.

Step 2 - Connect Elbow to the Flange

Connect the ABS elbow to the toilet flange. The ABS elbow should be three inches in diameter, and it should have a 90-degree angle.

Step 3 - Rough-In Vent

Using a 1 ¼-inch polyvinyl chloride pipe, or PVC pipe, locate a vent no farther than five inches away from the flange. This will travel inside the finished wall. Leave room in this vent for connecting to the vanity and tub.

Step 4 - Install Cold-Water Supply

man in bathroom with piles of tools and plumbing supplies

Using copper piping, install the cold-water supply. Bring the PVC pipe up to 9 1/4 inches above the floor. Then, install a water shut-off valve and a ⅜-inch compression fitting for the flexible pipe to the toilet about six inches away from where the toilet will be installed.

Step 5 - Construct Drain for Drop-in Sink

There are two types of sinks that you can use in your bathroom: a drop-in sink or a pedestal sink. A drop-in sink should have a drain that is in the center of the sink and goes to 18 inches above the floor. Use a 1 ½-inch hub to fit to the 1 ¼-inch drain pipe in the wall.

Step 6 - Assemble P-Trap and Cleanout

Assemble a PVC P-trap and a cleanout underneath the drainpipe to make it easy to clean out any clogs in the future. When finished, you should have made a 1 ¼-inch drain pipe that goes between the waste pipe and the sink.

Step 7 - Add Water-Supply Lines

plumbing beneath a bathroom sink

Using copper supply lines from the hot and cold pipes already in position, make sure the lines are center with the sink faucet and at least 21 inches from the floor. Place ⅜-inch compression fittings on the ends to connect them to the faucet handles.

Step 8 - Install Drain on Pedestal Sink

With a pedestal sink, you must bring the waste-water pipe directly underneath the sink itself. Bring the rough plumbing up to 18 1/2 inches off the floor, and center it with the sink’s drain.

Remember to keep all of the P-Traps and cleanouts close to the drain to keep them hidden within the pedestal.

Step 9 - Install the Water Supply

Bring water-supply tubes up from the wall at a right angle and 18 inches off the floor. Fit it with a 3/8 inch compression fitting on the end. After the rough plumbing is taken care of, make sure the wall has the necessary support to hold the sink upright.

How to Install Rough-in Plumbing for a Bathroom, Part 4 >>