Pump, Primer 2 : exhaust ejector. A valve diverts the engine ehaust through a venturi ejector, lowering the pressure in the centrifugal pump chamber, so that atmospheric pressure will force the water into the pump and thus prime it
H. J. Porter (Chairman - Technical Committee), Dictionary of Fire Technology, The Institution of Fire Engineers, The Victory Press (Leicester) Ltd. 1979 UK. (Fr Tech - Brit) {81}