5.1 Each element has unique flow patterns and each element has unique hydraulic characteristics (that is, flow and head loss). In addition, each element may exhibit variable hydraulic capacity as the element filters become occluded, the filter media swells or shrinks, and water viscosity (that is, water temperature) changes. In some cases filters experience hysteresis with respect to filling and emptying. The testing procedure in Section 7 will help develop the parameters necessary to determine the hydraulic capacity of an element at one instance in time. The test can be repeated at desired time increments to determine how the hydraulic capacity varies over time.

1.1 This test standard shall be used to determine the hydraulic characteristics of stormwater filtration elements.

1.2 Elements tested shall be of a size commonly manufactured, not a scale model.

1.3 The position and orientation of all filter elements during testing shall be identical to the position and orientation used during normal operation.

1.4 The direction of flow during testing shall be identical to the direction of flow during normal operation.

1.5 As each stormwater treatment device is unique in design and hydraulic capacity, a sufficient number of accurately measured data points are needed to properly define the hydraulic characteristics of each test element. Therefore, it is imperative that the element setup and subsequent testing methodologies be well defined and executed to assure accurate flow and elevation data.

1.6 This test determines the hydraulic capacity of stormwater filtration systems. Test results are not an indicator of the filtration performance with respect to the capture of solids or other materials.

1.7 Units—The values stated in either SI units or inch-pound units are to be regarded separately as standard. The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other. Combining values from the two systems may result in nonconformance with the standard.

1.8 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety, health, and environmental practices and determine the applicability of regulatory limitations prior to use.

1.9 This international standard was developed in accordance with internationally recognized principles on standardization established in the Decision on Principles for the Development of International Standards, Guides and Recommendations issued by the World Trade Organization Technical Barriers to Trade (TBT) Committee.