Turn off the water supply valve behind the toilet
Flush the toilet to empty the tank and bowl
Check the supply line for loose connections or damage
Tighten the supply line fittings if needed
Inspect the tank bolts for leaks
Tighten or replace tank bolts and washers if leaking
Check the flapper for wear, warping, or debris
Clean or replace the flapper if it is not sealing
Inspect the fill valve for cracks or faulty operation
Replace the fill valve if necessary
Check the flush valve seal for damage
Replace the flush valve seal if worn
Inspect the wax ring at the base of the toilet
Replace the wax ring if water leaks from the floor
Tighten the closet bolts at the toilet base if loose
Reseat the toilet if it rocks or shifts
Check the tank-to-bowl gasket for leaks
Replace the gasket if damaged
Turn the water supply back on
Test the toilet for leaks after each repair
Call a plumber if the leak continues