Patent ID: 8127448

Claim:
A method of making a preassembled drainage unit comprising the steps of forming a continuous web of membrane material about one side of a longitudinally extending barrel with longitudinal edges thereof splayed outwardly; forming a continuous web of net material about an opposite side of the barrel with longitudinal edges thereof splayed outwardly; securing said longitudinal edges of the membrane material to said longitudinal edges of the net material to form a sleeve having a first peripheral portion of net material, a second peripheral portion of water permeable membrane material and a pair of outwardly directed flaps; closing a forward end of the sleeve outside the barrel; moving the closed forward end of the sleeve longitudinally away from the barrel while passing a mass of light weight synthetic aggregate through the barrel and into the sleeve; and thereafter closing a back end of the sleeve outside the barrel after filling of a predetermined length of the sleeve with the aggregate to form the preassembled drainage line unit.