My behind
Adjust the flushometer / Fill valve / flapper
Put a new flapper in the tank. The flapper is what the handle is attached to. They get hard over time and don't seal completely so the tank drains and then refills.
remove and install a new filler valve and get a proper flapper for your toilet at a plumbing supply
New flush valve may be needed.
Check the flapper and re-adjust the fill height.
That is the 'flapper valve' in the bottom of most toilet tanks. This valve is pulled up when you flush, admitting water into the bowl.
An improved 'flushing' system for the toilet. In particular the ball valve system
There is no such thing as a "flushing tower" in America you have to go to France and ask for directions about changing a Douglas valve or fluid intake valve (Ball cock)
A loud whistling in the pipe after flushing the toilet may indicate that the shutoff valve needs to be replaced. Replacement valves are available at most home improvement stores.
More commonly called the 'flapper', it 's the valve that fits over the hole in the base of the tank that you activate when you press the flush lever.
This question is vague as what is needed is whether it is the inlet stopvalve, the inlet valve itself or flushing valve.
Take off the back of the toilet. Look down to the bottom and you'll see a flap that is raised when you flush it. That flap is leaking. IF the toilet is old I strongly recommend the Gerber viper toilet. Inexpensive and works great.ANS 2 - change the flapper valve - takes about 5 minutes and costs less than $5