Gravity Grease Separation

How gravity grease traps work

Fat, oil and grease has a lower specific gravity than water and as a consequence it floats on it’s surface. This principle makes a conventional grease trap extremely simple and very effective.

Typically a grease trap comprises of a chamber diveded by an integral baffle-wall. The wall runs from the top of the chamber to just short of it’s base so when the chamber is filled with water anything that floats on the surface will be trapped by the baffle and contained within the first section of the vessel.


The grease trap system separates fat, oil and grease as follows

  • Kitchen effluent passes into the chamber which slows the flow and allows the oil content to separate and float to the surface.
  • Separated oil is contained using the baffle wall and forms a layer on the surface.
  • ‘Cleaned’ water is allowed to pass under the baffle wall and onto the main drainage system.

This separation principle is employed in grease-traps ranging from indoor under-counter units to large below-ground systems and automatic grease separators .

Watling Hope supply grease traps for all applications from 20 litre stainless steel under sink units to 8000 litre underground separators.

Once installed the grease trap will require regular emptying using a vacuum unit to maintain its effectiveness or regular treatment using a biological additive (see grease treatment).

Safe Contractor British Water

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