A common problem with showers is a whistling noise when the water is running. This problem is not only a minor annoyance but can be a sign that worn parts need replacing. The whistling noise in a shower is caused by a malfunctioning showerhead or a worn-out diverter in the fixture. Unfortunately, it may not be apparent which is the problem, so replace the showerhead first as it's the easier repair.
Grasp the water pipe on which the showerhead is attached, using a pair of slip-joint pliers.
Hold the pipe steady and turn the base of the showerhead counterclockwise, using another pair of slip-joint pliers. Loosen the showerhead enough to remove it by hand.
Clean the threads on the water pipe using a piece of steel wool. Lightly rub the steel wool over the threads to remove debris and mineral deposits.
Wrap the threads with Teflon tape to help seal the connection. Wrap the tape clockwise around the threads.
Screw the new showerhead onto the threads by hand to ensure it doesn't cross-thread. Tighten the head, using the two slip-joint pliers as you did when you removed the old one. Do not overtighten.
Locate the shut-off valves behind the shower and turn them off. Sometimes there is an access panel in another room behind the shower. If you cannot find shutoffs for the shower, turn off the main water supply for the house.
Remove the handle on the fixture by removing the set screw at the base with the proper size Allen wrench. Pull off the handle once the set screw is removed. Some fixtures have a metal or plastic collar that is pulled off by hand.
Unscrew the diverter, using a valve stem wrench. Place the valve stem wrench completely over the body of the diverter and turn it counterclockwise until you can remove the diverter by hand.
Smear plumber's grease on the new diverter and in the fixture cavity. Screw the diverter into the seat at the bottom of the cavity by hand to ensure it doesn't cross-thread. Turn the diverter clockwise to install. Finish tightening the diverter, using the valve stem wrench.
Replace the collar, if applicable, and reinstall the handle. Restore the water supply to the shower.