1.1 This specification covers water well casing pipe and couplings made from thermoplastic materials in standard dimension ratios (SDR), SCH 40 and SCH 80.1.2 Specifications are provided for the application of these materials to water well and g This specification covers water well casing pipe and couplings made from thermoplastic materials in standard dimension ratios (SDR), SCH 40 and SCH 80. Well casing is produced in either plain end, belled end, or threaded, and is used for water wells, g