Step 4 · Install the Drain Stub-Out
At the vanity location, install a 1.5-inch PVC 90-degree elbow onto the drain arm inside the wall. Cut a short piece of 1.5-inch PVC pipe (the stub-out) long enough to extend about 4-6 inches past where the finished wall will be. Use primer and cement to glue this stub-out into the elbow. Finally, place a temporary test cap on the end of the stub-out to prevent debris and sewer gas from entering the room.