This document gives the definitions and specifies the minimum requirements for injection moulded, compression moulded, extruded and thermoformed thermoplastics arch-shaped chambers, including integral components, used in underground systems for retention, detention, transportation and storage of non-potable water (e.g., storm water) and manufactured from polyethylene (PE) and polypropylene (PP). These chambers are intended for buried underground use in one horizontal layer, e.g., in landscape, pedestrian or vehicular traffic areas. In the case of detention and retention systems, the main purpose of the chambers is to retain water, for later infiltration in the ground or for later use in non-potable applications (irrigation, cleaning, sanitary facilities, etc), or to detain water during a storm, transferring it in a controlled way to the public storm water network. Applications include commercial, residential, agricultural, and highway drainage, including installation under parking lots and roadways. Product properties are determined by a combination of material specifications, design and manufacturing process. These chambers are intended to be used as elements in a modular system where the manufacturer has clearly stated in the documentation how the components are assembled to create a complete retention, detention, transportation or storage system.