INTRODUCTION This Item presents a method for estimating the size*@ efficiency and typical flange sizes of a pump suited to a given duty. It may be used with the other Items in the series that give guidance to the non-specialist on the selection of pumps. The other Items in the series are as follows. Radial@ mixed and axial-flow pumps. Introduction@ Item No. 80030 Radial@ mixed and axial-flow pumps. Glossary of terms@ Item No. 81001 Radial@ mixed and axial-flow pumps. Conversion factors@ Item No. 81002. * The method provides an estimate of impeller diameter which is often used by manufacturers as a designation of the pump size.