When replacing your standard bathtub with a new unit, sometimes it is necessary to relocate the tub drain pipes. Many bathtubs now come with a drain in the right corner of the bathtub instead of in the middle. Moving a bathtub drain from the center to the right side requires accessing the plumbing pipes under the sub-floor. The old tub must be removed before the drain is moved.
Things You'll Need
2 PVC elbows
PVC tub P-trap
Set the bathtub in place. Mark the drain hole of the tub onto the sub-floor with a pencil. Remove the tub and set it out of the way until you are ready to re-install it.
Run a stud finder along the sub-floor and locate the floor joists. Mark the centers of each floor joist. Measure from the front wall to the center of the new hole with a tape measure. Write the measurement down. Measure from the side wall to the center of the new hole and mark that measurement down. This helps you locate the center of the drain once you remove the sub-floor.
Draw a rectangular box from the front wall to the joist that is past the new drain hole, with the two sides of the rectangle 1 foot and 3 feet from the side wall. Place a level across the center of the new drain hole with the ends pointing to the sides of the rectangle tracing. Mark lines on the outside of the sides of the rectangle to mark the center location of the drain pipe.
Adjust the depth of your circular saw to 1/4-inch. Cut the outline of the sub-floor with the saw and remove the cut piece of floor away from the work area.
Cut the P-trap of the old bathtub drain pipe off the straight piece of drain pipe with a hacksaw. Cut enough off the straight piece of pipe that it is 6 inches from the center line of the new drain location.
Place a PVC elbow on the end of the drain pipe with one end pointing to the new drain area. Measure from the side wall to the center of the new drain location. Use the measurement you wrote down for the center of the drain from the side wall. Make a mark on the exposed floor joist at the location with a pencil.
Measure from the elbow to the mark. Cut a piece of straight PVC to the measurement. Insert the straight piece of PVC into the open end of the elbow. Slip a new elbow on the opposite end of the straight pipe. Attach the new P-trap to the elbow. Check the measurement once more to ensure the open end of the P-trap is at the center mark of the new drain location.
Disassemble all of the new PVC pipes. Prime the outside ends of the straight pipe with PVC primer and also the inside ends of each elbow and the P-trap.
Apply PVC cement over the primer areas of each part and fit them all together, starting with the elbow on the existing drain pipe.
Grab the piece of sub-floor you cut out and drill the tracing for the new tub drain with a hole saw. Place the cut piece of sub-floor back into place. Drive finishing nails through the sub-floor and the floor joists with a hammer to secure the cut piece.
It might be necessary to drill a hole through a floor joist to redirect the tub drain line. An angle drill with a 2-inch hole saw works perfectly if this is necessary.