Grease separators are dedicated to treat municipal sewage in respect to fats produced at the bars, restaurants, catering facilities, food and meat processing plants etc. The separators trap the organic suspensions and animal and vegetable fats. The devices are dedicated to underground installation irrespective of the load class and for installation above the ground. These separators can be equipped with an integrated settling tank and other supplementary elements constituting additional accessories of the device. The enclosure of the devices produced on the basis of a Weholite structural pipe in various ring stiffness classes adapted to water-soil conditions.