Bathtub diverters sit in the tub's faucet, where you must pull up on the post on the top of the spout to divert the water to the shower head. When the diverter becomes stuck, you might be forced to take a bath instead of a shower or vice versa. If you cannot successfully loosen the diverter, you will have to replace the entire spout.
Fortunately, both procedures are relatively straightforward and will take anywhere from five to 15 minutes, not including the time it might take to purchase a new spout.
How to Loosen a Bathtub Faucet Diverter
Spray penetrating lubricant into the spout opening so it hits the diverter piece. Spray the penetrating lubricant around the post on the top of the water spout and wait five minutes or more before trying the diverter again.
If this does not work, replace the spout.
Removing a Bathtub Spout
Remove the bathtub's spout to replace it and the diverter. Look over the underside of the spout with a flashlight, looking for a small screw that may hold the spout on the water pipe. Remove the screw on the underside of the spout, if one is present, using an appropriately sized Allen wrench. Pull on the spout as you wiggle it left and right to remove the spout from the water pipe.
Clamp a pipe wrench to the old spout if you do not see a screw. Turn the entire spout counterclockwise with the wrench until the spout unthreads from the water pipe.
Installing a New Spout
The replacement spout needs to have a diverter in the same spot as the old spout and it must attach to the water pipe that same way as the old spout. Bring the old spout with you to your local hardware store to ensure you purchase a match.
Slide the new spout onto the water pipe and tighten the screw on the spout's underside. If the water pipe has threads, clean them with a wire brush and wrap pipe tape clockwise around them.
Thread the new spout onto the pipe by hand, wrap the spout with a thick towel and clamp the pipe wrench to the spout so you can turn it clockwise until the back of the spout touches the tub and shower surround.
Test that the new spout and diverter work correctly by turning on the water and pulling the diverter up until the water comes out of the shower head, then pushing it down again to release the water from the spout. If the new diverter does not seem to work well, it may not match the original spout.