Liquid differential pressure measurement apparatus using at each of two separate vertical locations a manifold with a pair of voids, each pair being covered with a thin, non-elastomer membrane pressing tightly against a horizontal fence line therebetween. A first void of each pair is gas pressurized from the external side of the manifold to move the membrane on the internal side of the manifold outwardly against the pressure head of liquid on the membrane at the location of the fence line, the gas escaping via the second void, which is vented. A meter connection to the first void of each pair is supplied to a differential pressure meter and/or a device that converts a differential pressure to an electrical signal for remote readout or the like.