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RIW Double Drain is a cold applied, impermeable, high density polyethylene profiled sheet incorporating a permeable geotextile filter fabric. It is designed to prevent ground water reaching a structure and to enhance the performance of the waterproof membranes. Double Drain can be used in conjunction with a primary waterproofing system or on its own to isolate the structure from the surrounding soil and relieve hydrostatic pressure, by promoting the flow of ground water away from the face of the structure to land drainage. The Double Drain system can also be used to provide excellent protection to a primary waterproofing system, against backfilling and mechanical damage.