The Lubachów storage reservoir was built in the 1920’s. It is equipped with a relatively complex outlet installation, operating in variable hydraulic regime. The discharge deviations curves elaborated by German engineers for individual devices, after verification turned out to be burdened with a comparatively big error. This concerns especially the front spillway as well as intermediate outlets, and to a smaller degree the bottom outlets. The authors made a detailed analytical verification of the outlet installations and found great deviations from the currently valid discharge curves for these devices. Based on the analysis of conditions of computational discharges passage through the reservoir, they proved a high potential threat of water flow over the dam crest.