The tub spout you have with the knob on the end of it is a shower diverter. The knob diverts water away from the tub spout and up to the shower head. In your case, the diverter needs to be replaced.

Question: The bathtub knobs for hot and cold water are separate and there is a stopper to allow the water to go to the shower. Replace Tub Spout for a Better Shower - Los Angeles Times ...

I have a tub spout where I pull up on the handle to start the shower. Anything you can tell me would be most appreciated. – Scott H., Spokane A: Since the showerhead eventually stops dripping ...

In the tub spout diverter, a small gate valve is attached to the base of a plunger shaft located in the spout. It is held in the up position for the shower by water pressure.

Replacing a shower diverter problem is easy and inexpensive. If all goes well, there will be plenty of water coming out of the showerhead in about 30 minutes.

The diverter valve can wear out due to constant use and exposure to water, leading to a leaky shower faucet. When this valve deteriorates, it may fail to seal properly, causing water to leak from ...

♪♪ Kevin: On "Ask This Old House," our experts travel across the country to answer questions about your house. ♪♪ Today, when this tub spout is open, water pours out the shower head ...