Eljen GSF Geotextile Sand Filter
How the Eljen GSF System Works
The Eljen GSF Geotextile Sand Filter System is a cost-effective upgrade from other septic technologies. Comprised of a proprietary two-stage Bio-Matt™ pre-treatment process, the GSF Modules apply a better-than-secondary aerobic effluent to the soil, increasing the soil’s ability to accept the effluent. The result is superior treatment in a smaller soil absorption area.

Primary Treatment Zone
Perforated pipe is centered above the GSF Module to distribute septic effluent over and into corrugations created by the cuspated core of the GSF Module.
Septic effluent is filtered through the Bio-Matt fabric. The GSF Module’s unique design provides increased surface area for biological treatment that greatly exceeds the Module’s footprint.
Open air channels within the GSF Module support aerobic bacterial growth on the Module's geotextile fabric interface, surpassing the surface area required for traditional absorption systems.
An anti-siltation geotextile fabric covers the top and sides of the GSF Module and protects the Specified Sand and soil from clogging, while maintaining effluent storage within the Module.

Secondary Treatment Zone
Effluent drips into the Specified Sand layer and supports unsaturated flow into the native soil. This Specified Sand/soil interface maintains soil structure, thereby maximizing the available absorption interface in the native soil. The Specified Sand supports nitrification of the effluent, which reduces oxygen demand in the soil, thus minimizing soil clogging from anaerobic bacteria.
The Specified Sand layer also protects the soil from compaction and helps maintain cracks and crevices in the soil. This preserves the soil’s natural infiltration capacity, which is especially important in finer textured soils, where these large channels are critical for long-term performance.
Native soil provides final filtration and allows for groundwater recharge.

GSF Geotextile Sand Filter Cutaway