An improved process for removing polymeric by-product (ASO) from the HF alkylation acid in an HF alkylation unit used for the production of gasoline boiling range alkylate product by olefin/iso-paraffin alkylation, comprises fractionating a portion of the circulating HF alkylation acid inventory of the unit with a portion of hot alkylate product in a fractionation zone to from an overhead product comprising HF alkylation acid and water and a bottoms fraction comprising the polymeric by-product and alkylate. The bottoms fraction is sent to the isoparaffin stripper of the unit to remove trace HF alkylation acid as overhead and form a product stream of hot alkylate as a bottoms fraction.