The present invention relates to a polymerization process for producing olefin polymers in a loop reactor comprising the steps of: introducing into the loop reactor one or more olefin reactants, polymerization catalysts and diluents, and while circulating said reactants, catalysts and diluents, polymerizing said one or more olefin reactants to produce a polymer slurry comprising essentially liquid diluent and solid olefin polymer particles, said process further comprising one or more cycles of: (a) allowing said polymer slurry to settle in one or more setting legs connected to said reactor, and (b) discharging from a setting leg a predetermined volume of polymer slurry substantially equal to the volume of polymer slurry settled in said settling leg since its previous discharge.