During heavy downpour, the Labko FRW Basic (Flow Regulation Well) adjusts the incoming flow in the separator system to dimensioned flow of the separator system. Labko FRW basic contains a flow adjustment plate, which provides an even flow into the separator, even if the incoming flow should exceed the dimensioned flow of the separator system. The excess flow is directed via the bypass pipe to pass the separator system. This prevents the washout of the gathered sands and oils in the separator system.