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Oil and grease separators

Grease separators

A grease separator is used in industrial and catering establishments from which the fats and oils of plant and animal origin can be poured into the environment. Their use is mandatory in large kitchens, hotels, hospitals, restaurants, foodstuffs, slaughterhouses, meat processing plants, etc. The grease separator complies with the SIST EN 1825-1 standard and consists of two parts, the sludge settler and the fat collector. In the sludge ditch, the waste water stream settles down, and the heavier particles settle to the bottom. In the fat reservoir, however, oils and fats with a lower density are separated from the water and retained on the surface. Purified water flows into the knee at the outflow, which is submerged below the level of fat and oil.

Grease separators are designed for underground installation. You can find instructions on how to buy on the manufacturer's website www.roto.si. In case of doubt, contact the manufacturer. For dimensions larger than NG20, contact the manufacturer.


Our grease separators are made from environmentally friendly polyethylene (PE), which is suitable for sewage and clean water. It has a long life and low weight, and resistance to most aggressive domestic materials (oils, fats, house cleaners, ...).

Determinate size

The size can be calculated using the formula NG= Qs¸*fd*ft*fr*fm
QS - quantity of sewage water
fd - fat density factor, if this is greater than or less than 0.94 g / cm3
• ft - the temperature factor, if greater than 50 ° C, increases
• fr - detergent factor
• fm - the factor of increased extracted fats (slaughterhouses, processing).


produced by a European manufacturer in accordance with standard BS EN 1825-1, made from durable, hard polyethylene (LLDPE), has a long lifetime, 100% recyclable, are waterproof, quick and easy installation (light weight, no need for a crane (when placing in a pit), panelling, no need for masons, concrete mixers, etc.)., easy maintenance, low operating costs and competitive prices.

Grease separators NG2-NG20

Traps and separators allow fats and grease to naturally (principle of gravity) separate out from water.

Oil separators

Oil separators are tanks in which water, mineral oils (hereinafter referred to as oils) and hard particles (silt, sand, ...) are separated. Mineral oils include all propellants, lubricants, oils with a density of less than 0.95 g / cm³. Oils can be used to clean water in closed (mechanic workshops, production, gas stations) and open spaces (parking lots, loading platforms, landfills).
Installation and usability

The oil separators are only for the purpose of underground installation. The installation must be made in accordance with the manufacturer's instructions. Oils separators are not suitable for the treatment of industrial waste water (acids, bases, aggressive chemicals, ...). The oils are hiking (up to 250 kg / m²). If we install a relief-reinforced concrete slab and cast iron housings above them, they are suitable for driveways / roads.


The tank, the inner part, the inlet pipe, the outlet pipe, the extension and covers are all made of environmentally-friendly polyethylene, which can be fully recycled. Polyethylene also assures the water tightness of the tank. The coalescence filter of the mushroom structure is mounted on a wall that separates the chamber. The material is resistant to aggressive environmental influences, such as changing temperatures, etc - the characteristics of the material will not change across the seasons. Each oil separator is subject to internal control of material and production from implementation to customer.

Determining right size of oil separator

For correct determination of oil separators, it is necessary to know the following data:
Location of installation of oil separator
The surface from which the water flows into the oil separator.
Purpose of surfaces from which the water flows into the oil catcher.
The type of waste water that flows into the oil catcher (rain water that washes the surface, water from mechanical workshops, ...)

Selection of the appropriate trap

Determining the size is made by calculation Ns= (Qr+fx*Qs)*fd
Ns- The nominal size of the oil separator in l / s.
• Qr- Maximum rainwater flow from the return period of precipitation for a given location in l / s.
• Qs- Maximum flow of waste water in l / s.
• fx- The retention factor, depending on the surface from which the water flows into the oil separator (between 0 and 2).
• fd is a density factor that depends on the type of mineral oil (between 1 and 3).

Procedure of separating waste water

  1. Waste water flows from the surface to the oil inflow pipe of the oil separator.
  2. The inflow pipe is designed to disperse water.
  3. In the first chamber is settling, hard particles are loading at the bottom of the chamber.
  4. The water that is still mixed with oil is passed through a coalescing filter. Due to the structure of the filter, the flow of water slows down and the separation of water and oil starts. Small drops of oil begin to aggregate into larger. As the oil density is lower than the water density, due to the increased volume of the drops of oil, they start to rise to the surface of the second chamber
  5. Purified water flows into the outflow, which is designed to hold the oil. It is also possible to install an automatic lock on the outflow, which prevents spillage in the event of an excessive amount of oil.

According to the standard

SIST EN 858-1, SIST EN 858-2 and the Rules on the Decree on the emission of substances and heat in the discharge of waste water from sources of pollution Official Gazette RS 47/05. Basically, the separators are divided into two classes. Class I with a flow rate of up to 5 mg / l and II. class with a flow rate of up to 100 mg / l. Class I separators have a coalescence filter installed and are used where the meteor and process wastewater leak into surface waters or in the environment. Separators II. class are usually gravity and are used where meteor and process wastewater leaks into the sewer. The size of the separators is determined by the nominal number of NS, which is equal to the flow rate in l / s. Before installing the oil separator, we must ensure that the effluents at the inflow will not exceed 35 ° C.