If you have to jiggle the handle or your toilet randomly starts and stops running, a bad flapper is the first thing to check to get it to stop running. Before calling a plumber try replacing your flapper and see if that helps.
Your toilet flapper is in charge of flushing your toilet. It lifts when you push down the handle and lowers as the water drains. A bad one can’t seal right.
Step 1: Shut the water off at the wall and flush the toilet
Step 2: Disconnect the chain from the flush arm and remove the flapper
Step 3: Take the old flapper to the store and buy a replacement
Step 4: Clean the opening at the bottom of the toilet and install the new flapper
Step 5: Attach the chain to the flush arm
Step 6: Turn the water back on and test
If that doesn’t do the job, the next most common cause is a bad fill valve. Your fill valve is a tube that comes up inside the tank. It's usually connected to the water supply hose from the wall.
A really common give-away that the fill valve has gone bad is water spraying from the top. You might think that's how it fills the tank when you flush, but it's not actually normal.
Like the flapper, a fill valve is something that you can replace yourself. Its pretty straightforward, if a bit more involved than replacing a flapper. Check out the video below for steps on how to replace yours.