Turn off the water supply
Plug the drain
Remove the diverter handle or spout
Inspect the diverter for visible damage, corrosion, or mineral buildup
Clean the diverter parts with vinegar or a descaling solution
Replace worn washers, O-rings, or cartridges
Tighten any loose connections
Reinstall the diverter components
Turn the water back on
Test the diverter for proper flow between shower and tub
Replace the entire diverter if repairs do not fix the issue