Turn off the water supply to the bath tap
Plug the bath drain
Remove the tap handle
Unscrew and remove the valve or cartridge
Inspect the washer, O-ring, and cartridge for wear or damage
Replace any worn or damaged parts
Clean mineral buildup from the tap components
Reassemble the tap
Turn the water supply back on
Test the tap for leaks
Replace the entire tap or call a plumber if the leak continues