A container unit for brake fluid in a vehicle hydraulic brake system and connectable to a hydraulic component of the brake system, and includes: a storage chamber for brake fluid, the storage chamber having a flow channel between the storage chamber and the hydraulic component, the storage chamber and flow channel define an inner space of the container unit; a displaceable valve unit regulates flow of brake fluid in and out of the storage chamber through the flow channel, the valve unit in an open position is displaced to allow brake fluid to flow when the container unit is connected to the hydraulic component, and the valve unit in a closed position is displaced to prevent outflow of brake fluid when the container unit is disconnected from the hydraulic component. The valve unit in the open and closed positions is fully enclosed within the inner space of the container unit.