This European Standard specifies the required properties of the piping system and its components made from glass-reinforced thermosetting plastics (GRP) based on unsaturated polyester resin (UP) intended to be used for water supply (drinking or raw) with or without pressure. In a pipework system, pipes and fittings of different nominal pressure and stiffness ratings may be used together. NOTE 1 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. This standard is applicable to GRP-UP, with flexible or rigid joints (see 3.37 and 3.38), primarily intended for use in buried installations. NOTE 2 Piping systems conforming to this standard can also be used for non-buried applications provided that the influence of the environment and the supports are considered in the design of the pipes, fittings and joints. It is applicable to pipes, fittings and their joints of nominal sizes from DN 100 to DN 3000, which are intended to be used for the conveyance of water at temperatures up to 50 °C, with or without pressure. This standard covers a range of nominal sizes, nominal stiffnesses and nominal pressures. Clause 4 specifies the general aspects of GRP-UP piping system intended to be used in the field of water supply with or without pressure.