A liner for a horizontal well, the liner comprising a substantially hollow elongated body having a plurality of orifices in the liner body that each allow limited ingress of fluid into the liner body. Each orifice has a predetermined shape, size and spacing in the liner body. The shape, size and spacing of the orifices provide that pressure of fluid in an annular space located between the liner body and the horizontal well is substantially uniform along the horizontal well.

An underdrain apparatus and a method for manufacturing such apparatus are provided. The underdrain apparatus can be extruded in long sections as a unitary part. The underdrain apparatus may be extruded in various sizes, shapes, and materials. Further, the underdrain apparatus may include a passageway for transporting water to and from the filter media and/or air to the filter media. In some embodiments, apertures are formed in the underdrain apparatus during an extrusion process to provide a path between the passageway and the filter media.