User requirements for sewage pumps primarily include reliability, which depends on the pump design and timely maintenance, as well as efficiency. For sewage pumps, wear on flow components significantly impacts performance over time, causing even highly efficient pumps to lose efficiency quickly. This paper presents a comparison of the performance and flow analysis of a two-blade sewage centrifugal pump before and after renovation. The primary research objects were the impeller and the shroud seal. 3D optical scanning and reverse engineering were used to capture the real geometric parameters of the pump’s flowing parts. The investigation included numerical simulations for different flow rates, as well as physical experiments on a test stand. The most damaged areas were the leading and trailing edges of the impeller and the shroud seal. The pump was renovated by replacing the damaged hydraulic components with new ones. Numerical analysis revealed the structure of the flow, the locations and distribution of losses, and areas of erosion. Testing showed that the pump’s efficiency increased from 44% to 68%, approaching its nominal efficiency. Furthermore, the pump’s flow rate at the BEP increased from 390 m3/h to 506 m3/h. Volumetric efficiency increased from 70% to 95%, and hydraulic efficiency increased only from 68% to 73%. These results demonstrate that wear of shroud seal has a more significant influence on pump operating parameters and efficiency while increasing energy consumption, than wear of the impeller.