While showers are generally dependable, a malfunctioning diverter valve on a tub-shower combination prevents changing the water from the tub spout to the showerhead. Installing a new, low-flow showerhead with an older diverter valve sometimes causes problems. Replacing the tub spout with a new one usually fixes either problem.
Some tub spouts and diverter valves attach to the pipe coming out of the wall using a setscrew. Removing these spouts requires loosening the screw and gently pulling and twisting the valve to pull it off the pipe. Once the old spout is off the pipe, the new one slides into place and attaches by tightening the screw.
The second method of replacing the diverter valve involves unscrewing the spout. Grasp the spout, and turn it counterclockwise to unscrew it. If the valve is difficult to move, inserting a hammer handle into the spout or attaching a pipe wrench provides the mechanical advantage to loosen it. Some of these pipes have the threaded section near the wall, and others have it near the end of the spout. When choosing a replacement, it is essential to choose the spout that matches the one removed from the shower. After replacing the spout, turning on the water and pulling the diverter lever should activate the shower.