Corcoran Precast Tanks provides a full range of commercial and industrial oil interceptors to protect your property from oil spills & contamination.

Full Retention Interceptors

Full retention oil interceptors are used in sites with a medium to high risk of oil spills or contamination. Examples include; maintenance garages, goods vehicle parks, refuse recycling etc. Full retention oil interceptors treat the full flow that can be generated by rainfall with an intensity of 60mm/h.
There are three types of Full retention oil interceptors:

1. Class 1- Full retention with coalescence filter and Automatic shut-off (where there is a high risk of an oil spill)

2. Class 1 – Full retention with coalescence filter and without Automatic shut-off (where there is a medium risk of an oil spill) (where there is a high risk of an oil spill)

3. Class 2 – Full retention without coalescence filter or Automatic shut-off (Can only be used where discharge to a wastewater treatment system)(where there is a high risk of an oil spill)

Bypass Separators

By-pass oil interceptors have specified flow rates designed to fully treat flows generated from the majority of rainfall events. Flows generated from intense rainfall events in excess of the designed flow rates by-pass the interceptor. The first portion, which is heavily contaminated, is treated by the interceptor, while the extremely diluted flows are bypassed. These interceptors are used when it is considered an acceptable risk not to provide full treatment for high flows, for example, where there is a high risk of a large spillage and heavy rainfall occurring at the same time is minimal.

Forecourt Separators

Forecourt interceptors are full-retention interceptors specified to retain on site the maximum spillage likely to occur on a petrol filling station. They are required for both safety and environmental reasons and will treat spillages occurring during vehicle refuelling and road tanker delivery. The size of the interceptor is designed to retain the possible loss of the contents of one compartment of a road tanker, which may be up to 7600 litres.

Corcoran Precast Tanks interceptors are manufactured from steel reinforced precast concrete and are normally installed on a bed of cl804 stone and backfilled with the excavated material. This results in considerable savings on time and materials. Our service also includes delivery to site and off- loading into position.

If you’re interested in our oil interceptors, please contact us.


In principle, we design to four basic classifications; Full Retention, Bypass, Class I and Class II. Classes I and II pertain to the Eurocode ISEN858 (Separator Systems for Light Liquids Pt. 1). All our separator range are certified to EN858 Part 1.
Our designs comply with the requirements of the EPA Wastewater Treatment Manuals:

  • Preliminary Treatment: Part 5: Oils, Grease and Fats
  • Primary Secondary and Tertiary Treatment: Part II
  • IS EN858 Part1

All of our products are engineered to the customer’s requirements, using established design parameters. The designs are based on flow speeds, retention times, temperature and the settlement characteristics of the target materials. The tank structures are designed to BS8110, BS8007 and the Design Guidelines for Steel Fibre Reinforced Concrete Structures.

If you’re interested in our oil interceptors, please contact us.

Description of basic type - Class I & II

The European Standard EN 858-1 refers to two classes of separator and the performance results achieved under standard test conditions.

Corcoran Precast Tanks can supply and install the following range of Separators:

  • Bypass Separators (4.0 - 84L/sec)*
  • Full Retention Separators (3.0 - 60L/sec)*
  • Forecourt Separators (10,000L)
  • Wash Down Separators (3.0 - 80L/sec)*
  • Silt Traps
  • Grease Traps

* Larger flow rates and/or special parameters available on request

Oil Interceptors FAQ