This Technical Specification (CEN/TS) specifies recommended practices for the underground installation of piping systems made of glass-reinforced thermosetting plastics based on unsaturated polyester resin (GRP-UP), intended to be used for pressure or non-pressure water or sewerage applications and complying with, as applicable, EN 14364 and/or EN 1796. It is applicable to GRP-UP piping systems of nominal sizes from DN 100 to DN 4000 which are intended to be used for the conveyance of liquids at temperatures up to 50 °C and at pressures of 0,5 bar and greater. Design procedures, the determination of long-term safety factors based on a semi-probabilistic approach, surge allowance and allowable negative pressures for buried GRP pipe applications are addressed in CEN/TS 14807 [1]. Piping systems conforming to EN 1796 or EN 14364 can also be used for above-ground applications provided the influence of the environment and the supports is considered in the design of the pipes and joints. It is recommended to refer to ISO/TR 10986 [4] for guidelines for the installation of above-ground flexible jointed pipes. NOTE It is the responsibility of the purchaser or specifier to make the appropriate selections from these aspects, taking into account their particular requirements and any relevant national regulations and installation practices or codes.