A new fast dichromate method of water COD determination is proposed according to which a water sample premixed with a solution of dichromate in concentrated (95%) sulfuric acid is passed by pressure or vacuum through a glass column with a quartz packing heated up to 150–170°C during 3–5 min. The oxidation level of ϵ-caprolactam and adipic acid is 2–2.5 times more and the time of waste water analysis more than 30 times shortened as compared with the standard “reflux” and “semimicrotube” methods.