Abstract: This invention relates to the manufacture of flexible porous irrigation pipe having an essentially uniform porosity throughout its length which is produced by extruding an essentially moisture-free non-homogeneous, mixture of pre-vulcanized elastomeric particles such as reclaimed crumb rubber from vehicle tire treads in major amount and a thermoplastic polymer binder such as low-density polyethylene in minor amount. The mixture is intimately mixed and extruded from an unvented extruder through an annular extruder die at a precisely-controlled temperature and then through a lengthy cooling liquid bath, the rate of pull-off through the extruder die and liquid bath being maintained constant. The leak rate of the fluid delivered from the porous pipe is substantially uniform over a lengthy prescribed dimension exhibiting a delivery variation of less than about 5 percent per unit of length.