Land drain filter sleeves are used to protect underground perforated land drain pipes from becoming clogged up by sand and silt particles. Due to the innovatively knit fabric of the sleeve, only very fine soil particles are allowed pass through and into the land drain pipe and be discharged from the drain pipe alongside the water.Larger particles will be blocked by the fabric from entering the pipe and as a result they will bridge against each other on the sleeve which leads to improved permeability of the existing backfill surrounding the pipe. Therefore, these sleeves are a low cost alternative to expensive backfill materials.Land drain filter sleeves are easily fitted to a perforated pipe like a sock, requiring only one person and they can serve as a filter envelope that covers many different perforated drainage materials such as PVC, HDPE, steel and aluminium.