Replace a bathroom shower diverter valve on the tub spout by replacing the spout. Determine if the old spout is threaded onto the pipe or attached in another way by looking for a set screw. If no screw is present, use a pipe wrench around the spout or insert a small hammer handle into the end of the spout for leverage and turn to unscrew it. If there is a set screw, use the appropriate tool to loosen it.
Take the old spout to the home improvement store when purchasing a replacement. Manufacturers make two types of threaded spouts; one has the threads for the connection near the wall, whereas the other has them near the end of the spout. Choose the appropriate spout for the tub to ensure it fits.
Install the new spout by cleaning the threads of any debris and wrapping Teflon tape around the threads of the nipple. Start the new spout on the pipe and tighten it by hand until it is snug and the spout is pointing down.
For spouts that use set screws, clean the fitting coming from the wall, slide the spout into place and tighten the screw. For showers with three control knobs, the diverter valve is the center knob. It rarely requires replacement, but sometimes it is necessary to replace worn parts to stop drips.