This document gives the recommended practise for underground open trench installation and commissioning of thermoplastics piping systems to be used for the conveyance of water under pressure (in addition to EN 805) and for the discharge of wastewater under gravity (in addition to EN 1610) . In the field of non-pressure underground drainage and sewerage this is reflected in the marking of products by application code "U" and "UD": - outside the building structure (U); - both buried in ground within the building structure (application area code "D") and outside the building (application area code "UD"). This document covers also installation and/or connections to valves, manholes, inspection chambers, gullies and other ancillary components in piping systems. NOTE 1 Code of practise for pipelines for gas supply is covered by EN 12007-series . NOTE 2 Recommended practices for installation of plastic piping systems for soil and waste discharge within the building structure is covered by CEN/TR 13801 . NOTE 3 Practices for underground installation of rainwater infiltration and storage attenuation systems are covered by CEN/TR 17179 . NOTE 4 It is assumed that additional recommendations and/or requirements are detailed in the individual product standards. NOTE 5 If non-plastic components are part of the plastic system the manufacturer's instructions should be taken into account. Requirements and instructions concerning commissioning of systems can be found in EN 805 and EN 1610 and the relevant national and/or local regulations. This document gives specific additional recommendations for commissioning relevant for plastic piping systems. Attention is drawn to any relevant local and/or national regulations (e.g. health, safety and hygienic requirements).