Nowadays, there are enterprises that use a direct-flow cooling system without treatment of used water before discharging it into a water body. Most of these enterprises use outdated equipment in the cooling system (including oil cooling systems). As a result, there is a high probability of oil products getting into the natural water body. An oil product in a stream of water can be dissolved and undissolved (emulsion). The design of the flow damper proposed in this work is part of a functioning industrial water quality control system. The flow damper is designed to register undissolved oil products in the water flow from the cooling system of a CHP plant. Measurements are conducted at the control points. The research model includes the development of a solid model of the flow damper (including the analysis of its use in a natural environment modelled by software package with the possibility of CFD analysis) and the calculation of oil particles ascent time inside the damper. The result of the study is the design of the flow damper, which ensures oil film detection in the cooling system effluents discharged into the water body.