This Code defines procedures for field performance and acceptance testing of hydraulic turbines and pump-turbines operating with water in either the turbine or pump mode. This Code applies to all sizes and types of hydraulic turbines or pump-turbines. It defines methods for ascertaining performance by measuring flow rate (discharge), head, and power, from which efficiency may be determined. Requirements are included for pretest arrangements, types of instrumentation, methods of measurement, testing procedures, methods of calculation, and contents of test reports. This Code contains mandatory test requirements and various methods of measurement. Where multiple methods of measurement and procedures are permitted by the Code, prior written agreement as to the selected methods and procedures is required. The test procedures specified herein and the limitations placed on measurement methods and instrumentation are capable of providing a total uncertainty, calculated in accordance with the procedures of PTC 19.1 and of this Code, of not more than: (a) Power ±1.2%, (b) Flow Rate ±1.5%, and (c) Efficiency ±2.0%. Where favorable measurement conditions exist and best methods can be used, smaller uncertainties should result. Any test with uncertainties greater than the above shall not qualify as an ASME Code test. This Code contains recommended procedures for index testing and describes the purposes for which index tests may be used. This Code also contains Tables for (a) Acceleration of gravity as a function of latitude and altitude; (b) Vapor pressure of distilled water as a function of latitude and altitude; (c) Density of water at a given temperature and pressure; (e) Density of dry air; and (f) Density of mercury.