I turned off the water supply in my home to replace a valve,when i turned it back on and flushed the toliet air in the line caused the toliet to keep running
I have had this same issue with my toilet and it is quit annoying. So I hope this link below will help you resolve your issue. I hope this helps!
It seems unlikely that the air is the source of problem. If the toilet continues to "run", it typically means that the tank is continually calling for water. Water is being allowed to seep out of the tank other than when a user is flushing the toilet. First, check the actual flush handle. Is it getting stuck in "flush" position? Second, lift the lid off your tank and check to see if the flapper valve is making a tight seal. This is the most common issue and sometimes can be fixed simply by adjusting the length of the chain mechanism that connects the flapper valve to the flush handle.