Hub laterals/ scale traps/ collectors-distributors comprise many slot tubes (laterals). They are positioned in parallel connected to a central pipe (header), or, positioned in star-form and connected to a central collector hub. A distributor-collector system is used in a treatment vessel containing for instance resin, active carbon, catalyst or another molecular bed, to retain the treatment media in the vessel. Normally an assembly of header and laterals is used at the top of the vessel for in-flow distribution. Another one is used at the bottom of the vessel for collecting the treated out-flow. The distributor-collector system creates an optimal flow distribution of liquids or gases throughout the vessel and avoids creation of preferential paths.