The invention relates to a means for preventing build-up of electrostatic potential in a fluid container during filling and/or discharging. The fluid container comprises electrical insulating materials and a valve means through which filling and/or discharging occurs. Means for reducing and/or eliminating electrical and/or electrostatic potential build-up during filling or discharging of the container is arranged in conjunction with the container walls. Such means may for example be arranged in conjunction with the valve means, reducing and/or changing the flow velocity of the fluid and/or the flow direction of the fluid during the filling operation. The invention relates also to a method of avoiding build-up of electrical and/or electrostatic potential, the method comprising changing the direction of fluid flow at least once at the top end of the container, so that the flow of fluid into the container preferably becomes laminar and/or is depressurized and wherein the fluid flow velocity into the container is reduced.