This article presents a serial identification with collective size estimation strategy for multiple gross errors in linear steady-state data reconciliation. With use of the theory of gross error equivalency (Bagajewicz, M.; Jiang, Q. Comput. Chem. Eng. 1998, in press), an effective strategy for leak detection is also presented. The issue of exact identification of gross errors is discussed, and the conversion of gross error sizes between any two equivalent sets is formulated. Finally, the proposed strategy is tested and compared with existing approaches.