Leaking Bath Overflow Why Is My Overflow Pipe Leaking?

Why is my overflow pipe leaking? - leaking bath overflow

I've noticed that my overflow pipe leaking all the time. The only time he is no longer when filling the tank and we all ran out of hot water, but when the tank is filled, it starts to drip. Im not sure if it could be the swimmer, but then there is a way how to solve the problem, instead of buying a new or I just get a new one.