This CEN Technical Report lays down stipulations relating to installation conditions for sudden change in section or direction (elbows, tee fittings, junctions) and the most widely used accessories at the inlet and outlet of pumps (valves and fittings) in order to minimise the effect of disturbances in the flow of liquid thereby created upstream and downstream from the pump and on the operation of the pump. NOTE 1 – The recommendations given in this document permit to solve a majority of the most current cases. These recommendations relate to three aspects of installation: the fitting of the pump to pipework by convergent and divergent pipes; in the case of elbows, tees and branching, their direction with respect to the axis of the pump; the minimum clearances to be adhered to between a disturbing (elbow, valve, etc.) and the mounting flange of the pump. This document applies to the installation of rot dynamic pumps (centrifugal, mixed flow and axial flow) fitted in piping. It applies to pumps having intake diameters equal to or less than 500 mm. The recommendations may be adapted in agreement with the pump manufacturer for intakes having dimensions exceeding 500 mm or for special applications. This document is not applicable to pumps of which the inlet is located in reservoirs, sumps or tanks and which will be dealt with in a subsequent standard. The recommendations in this document are only valid under the following conditions: Newtonian fluids having a maximum viscosity of 2.10-4 m2/s; occluded gas content at pumping temperature and inlet pressure not exceeding 2 % by volume for water and 4 % for other fluids; solids content (small particle size, such as sand) not exceeding 1 % by volume, nor 1 % by weight; in piping with diameters D1 and D2 (see Figure 11), flow rate velocity, should be in the following ranges: 3 m/s to 5 m/s at inlet; 4 m/s to 10 m/s at outlet.