This document specifies general requirements, minimum performance requirements and test procedures for instrumentation used to measure either volumetric flow-rate and/or total volume passed of water in closed conduits. It covers all closed conduit instrument (CCI) technologies intended to operate in closed pressurized pipes and partially filled pipes. Requirements are expressed in volumetric units which may be converted to mass using the fluid density. It is recognized that for some CCIs certain tests cannot be carried out. The data obtained from the testing of CCIs in accordance with the requirements of the Measuring Instruments Directive [1] or EN ISO 4064-1 [2] can be used to meet, in part, the requirements specified in this document. However, for the avoidance of doubt, compliance with the requirements of this document does not equate to compliance with the requirements of the Measuring Instruments Directive or EN ISO 4064-1.