The series are self-priming centrifugal pumps, self-priming is achieved using an ejector, housed in the pump body.

The total delivery produced by the closed centrifugal impeller is sent only partly to the delivery opening. The remaining water is recirculated through the ejector, which is connected to the suction chamber and generates the necessary vacuum to self-prime the pump. When first starting the pump fill the body with water, without bothering to fill the suction piping and eliminate air pockets. When the pump is stared up the water in the pump boby circulates through the ejector and transfers any air from the suction to the delivery chamber, expelling it through the delivery piping. At the same time the vacuum thus generated causes water to rise in the suction piping, thus self-priming the pump. Since the self-priming system operates continuously, these pumps are practically unaffected even by the presence of large amounts of entrained air in the fluid being pumped. The series, based on past rolwal experience, is designed with particular attention to hydraulic efficiency and choice of materials. The result is a compact, quiet, high performance pump.