Replacing a bathtub-only faucet with a tub-and-shower setup (or converting a tub to include a shower) involves adding a diverter, installing a shower riser and head, and ensuring the valve is compatible. The exact steps depend on whether you’re upgrading trim only or modifying in-wall plumbing.

Before You Start: What to Confirm

• Existing valve type

• If it’s already a tub/shower mixing valve, you may only need new trim and a shower riser.

• If it’s tub-only, you’ll likely need to replace the valve.

• Wall access

• Access from behind the wall (closet, access panel) makes the job much easier.

• Local plumbing codes

• Many areas require pressure-balance or thermostatic valves for showers.

Tools and Materials

• Adjustable wrench, pipe wrench

• Screwdrivers, Allen key

• Pipe cutter (for copper/steel) or PEX tools

• Teflon tape, plumber’s grease

• Silicone sealant

• Shower riser pipe and shower arm

• Shower head

• Tub spout with diverter (if applicable)

• New tub/shower valve (if required)

Option A: Upgrade When a Tub/Shower Valve Is Already Installed (Simpler)

Step 1: Shut Off the Water

• Turn off the main supply or local shutoffs.

• Open the faucet to relieve pressure.

Step 2: Replace the Tub Spout

• Remove the existing spout.

• Install a diverter tub spout (pull-up or push-button type).

• Use Teflon tape on threaded connections.

Step 3: Install the Shower Riser

• Remove the valve trim.

• Confirm there’s a capped top outlet on the valve.

• Install a vertical riser pipe from the valve to the shower arm outlet.

Step 4: Install the Shower Arm and Head

• Thread in the shower arm.

• Attach the shower head and tighten gently.

Step 5: Reinstall Trim and Test

• Restore water.

• Test tub flow and divert to shower.

• Check for leaks.

Option B: Convert a Tub-Only Faucet to a Tub-and-Shower (More Involved)

Step 1: Shut Off Water and Open the Wall

• Turn off water and drain lines.

• Open the wall behind the tub (preferred) or from the front if necessary.

Step 2: Remove the Tub-Only Valve

• Disconnect hot and cold supplies.

• Remove the old valve body.

Step 3: Install a Tub/Shower Mixing Valve

• Mount a pressure-balance or thermostatic valve.

• Connect hot (left) and cold (right).

• Connect bottom outlet to the tub spout.

• Connect top outlet to the shower riser.

• Set correct rough-in depth for finished wall thickness.

Step 4: Pressure Test

• Cap outlets.

• Turn water on and check all joints.

Step 5: Close the Wall

• Waterproof as required.

• Patch and finish the wall surface.

Step 6: Install Trim, Spout, and Shower Head

• Install valve trim.

• Install diverter tub spout.

• Install shower arm and head.

Step 7: Final Test

• Verify smooth temperature control.

• Test diverter operation and flow.

• Check for leaks.

Common Mistakes to Avoid

When You Can’t Add In-Wall Plumbing

If opening the wall isn’t possible:

• Use a tub Spout Diverter + exposed riser kit designed for retrofit.

• These mount externally and avoid wall demolition, but aesthetics are more utilitarian.

Summary

To replace a bathtub faucet with a shower:

• If a tub/shower valve already exists: add a diverter spout, riser, and shower head.

• If it’s tub-only: replace the valve with a code-compliant tub/shower mixing valve, add a riser, then install shower trim.

Planning, correct valve selection, and proper rough-in depth are critical for a safe, leak-free result.