ELJEN ® The Modular Leach Field Sewage Treatment System

The Eljen GSF® is primarily used for leach fields where advanced treatment is needed to meet environmental needs. It is used in bed and trench designs.

The Eljen GSF® A42 (4-feet long by 2-feet wide by 7-inches high) requires a longer, thinner trench, which can be a benefit where site restraints and hydraulic needs are a prime consideration.


Eljen GSF leach field
  • Provides advanced treatment in 50% less space than aggregate systems
  • Proven reliable performance eliminates the need for complicated maintenance and maintenance contracts
  • Smaller size and streamlined design significantly reduces overall system costs
  • Long-term leaching capacity is 2 to 3 times that of similar systems
  • The only system that pre-treats leach field effluent with a patented two-stage biomat filtration process
Lightweight, recycled material

Made from lightweight recycled material, the GSF® leach field is engineered for superior strength. The Eljen in-drain, with its pre-fabricated modular units comprised of geotextile fabric and cuspated spacer cores, provides an alternative to conventional stone and pipe or chamber leaching systems.

Substantial effluent pre-treatment occurs within the biomat which develops on the 100-square feet of geotextile fabric and the 400-square feet of cuspated core surface area in each 12-square foot type B in-drain unit.

This internal passive pre-treatment protects both the soil long-term acceptance rate (LTAR) and groundwater quality while providing reduced system trench length or leach bed footprint. At 7" thick, in-drains provide the lowest product profile, thus reducing system finished grade.


Eljen's in-drain
  • Pre-treatment of effluent via a two-stage biomat
  • Greater long-term leaching capacity maintained
  • Smaller area required than conventional systems
  • Has lower site impact and requires less off-site fill
  • Fabricated of lightweight recycled materials
  • Excellent documented long-term track record
  • 10-year warranty

Laboratory analysis of treated effluent extracted from below the in-drains has confirmed Eljen's claims of substantial effluent pre-treatment (over 50% BOD reduction) provided by the biomat at the geotextile fabric and cuspated core surfaces.

In-drains installed in a 6-inch layer of washed concrete sand can provide secondary treatment for typical septic tank effluent.

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Geotextile Sand Filter (GSF®)

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Geotextile Sand Filter

Design & Installation Manual

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