This document specifies general requirements and parameters for the pilot test evaluation of corrosion and scaling control additives in open recirculating cooling water systems. This document covers parameters including test unit design, operation, water quality and contamination. It also covers the design and operation of pilot test devices as well as parameters to be evaluated in pilot test units. This document covers the criteria that are used in pilot scale testing programmes for selecting water treatment programmes for specific recirculating cooling water systems. This document is only applicable to open recirculating cooling water systems. It does not apply to closed cooling systems and once-through cooling water systems. This document applies only to systems that incorporate shell and tube heat exchangers with standard uncoated smooth tubes and cooling water on the tube side. This document does not apply to heat exchangers with shell-side water, plate and frame and/or spiral heat exchangers and other heat exchange devices. However, when the test conditions are properly set up to model the surface temperature and shear stress in more complex heat transfer devices, the test results can predict the results of operating heat exchangers of that design. The test criteria established in this document are not intended to govern the type of bench and pilot scale testing normally carried out by water treatment companies as part of their proprietary product development programmes. However, water treatment companies can choose to use the criteria in this document as guidelines in the development of their own product development test procedures.