Hydraulic Institute Guideline for Rotodynamic Pump Efficiency Prediction HI 20.3–2015 helps users, specifiers, and purchasers of pumps understand what variables, design, and selection factors affect efficiency of rotodynamic pumps. Users will be able to calculate normally attainable efficiency and uncertainty band for variety of pump types. Efficiencies shown in guideline are those generally obtained using common manufacturing practices and are based on survey of pump manufacturers.