The study object was Lake Kortowo, restored since 1956 by withdrawing nutrient-rich hypolimnion water directly to the outflow by means of a pipeline. The studies were carried out after limiting the water flow in the pipeline from 0.25 m3·s-1 to 0.05 m3·s-1. The nutrients budget analysed in detail for the period of the pipeline operation was later compared to the theoretical budget with a surface outflow only. The maximum reduction of nutrients, and phosphorus in particular, was noted in the second half of summer stagnation when the pipeline was operating. Negative phosphorus accumulation in the summer months was the result of a balanced removal of hypolimnion water through the whole summer stagnation.