Abstract: A pneumatic liquid level sensing apparatus for marine tankers has a dip tube which by having air or gas applied to it bubbles into the liquid in a tank and produces a back pressure corresponding to the depth of the tube in the liquid, a pressure responsive valve device responsive to the back pressure relays a signal to a remote indicator and the provision of a balance pipe above the surface of the tanker liquid connected to a balancing input of the valve device enables the output of the valve device to be independent of the value of the air or gas pressure in the tank.