Gravelless pipe is an option for a conventional mediafilled land application system' In this system,

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• Gravelless pipe is an option for a conventional
  media-filled land application system. In this
  system, an 8- to 10-inch corrugated polyethylene
  pipe is wrapped with a geotextile fabric and
  buried in soil. The fabric acts as a biomat
  interface and a wick, evenly distributing
  wastewater around the circumference of the pipe.
  It also works to prevent backfill from entering
  the discharge holes on the pipe. The chief
  advantage to this type of system is that the pipe
  is flexible and lightweight. It may be placed in
  curved trenches fitting a specific elevation on a
  sloping site. However, it requires proper sizing
  and control of effluent quality (i.e., no scum or
  solids) to prevent excessive build-up of biomat
  on the geotextile fabric wrap.