Abstract: A fluid flow director for use in a water treatment system is provided. The fluid flow director is defined by a plastic sheet made up of a plastic substrate with a protective coating. The plastic substrate has fasteners disposed along two parallel edges thereof and the protective coating is substantially opaque to UV light. The plastic sheet is configured to be helically rolled such that the fasteners align and sealingly mate to form a tube. The fasteners are sized, constructed, and arranged to sealingly mate to form a substantially water-tight seam therebetween. In one embodiment, the plastic substrate is polyethylene and the UV opaque coating is polytetrafluoroethylene (“PTFE”).