Turn off the water supply valve
Flush to empty the tank and bowl
Check for leaks around the base, tank, and supply line
Tighten loose bolts, nuts, and fittings
Replace a worn flapper if the toilet runs continuously
Adjust or replace the fill valve if the tank overfills or will not refill properly
Clean or replace the flush valve if flushing is weak
Clear clogs with a plunger
Use a toilet auger for stubborn blockages
Replace the wax ring if there is water leaking from the base
Replace cracked or damaged tank parts
Replace the supply line if it is leaking
Reinstall the tank lid and test the toilet
Turn the water supply back on
Call a plumber if the problem persists