How to Bypass the Middle Knob on a Bathtub Faucet | Home Guides

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The middle knob or lever is the water diverter for the bathtub.

The middle knob on a three-knob bathtub faucet changes the direction of the flow of water from the bathtub faucet to the shower head. When the middle knob stops working, is frozen in place, hampers the flow of water to the bathtub faucet, or causes water to pour out of the bathtub faucet while the shower is running, it is typically the gaskets on the diverter valve that need to be replaced. The simplest way to bypass problematic middle knob and get your bathtub faucet to work correctly is to replace the diverter valve on the bathtub faucet.

1

Turn off the water supply to the bathtub and shower. Remove the screw on the shower diverter knob and pull off the knob. If the knob does not come off easily, it may have corroded or rusted in place on the shower knob stem. In this case, you will have to carefully pry off the handle with a large, flat-blade screwdriver.

2

Use a plumbers wrench to remove the threaded metal sleeve tube of the shower knob stem. Cut the caulk that was used to adhere the metal cover plate to the shower tile wall with a box knife and then remove the metal cover plate. Remove any remaining caulk from the back of the metal cover plate.

3

Use the plumber's wrench to unscrew the shower diverter and remove it from its seat in the pipe. The shower diverter is a cylinder with two rubber O-rings or gaskets on it.

4

Insert the new shower diverter valve into its seat in the pipe and hand tighten it. Turn the shower diverter valve a quarter turn with the plumber's wrench to secure it in place and form a seal with the O-rings.

5

Turn on the water supply to the bathtub and shower. Test the bathtub faucet by attaching the middle knob to the end of the shower diverter valve to ensure that you installed the new diverter valve properly. When done correctly there will be no visible leaks from the middle knob, and the water will flow from the bathtub faucet or the shower head, depending on which is selected when the water faucets are turned on.

6

Run a thin bead of caulk around the back rim of the metal cover plate and slide it on the diverter valve's stem and press it against the tile. Reinstall the metal tube sleeve knob stem and the middle knob of the bathtub faucet.

Things You Will Need

• Large flat-blade screwdriver
• Plumber's wrench
• Box knife
• Shower diverter valve
• Plumbing caulk

Tips

• There is no way to truly "bypass" the middle knob of a bathtub faucet and replace it with a two handled faucet set without completely re-doing the plumbing of the bathtub and shower fixtures.
• It is normal for a pencil-thin stream of water to come from the bathtub faucet when using the shower.

Warning

• Take care when cutting caulk with a box cutter or using tools to pry off old plumbing parts to avoid injury.