Bypass Separators

Bypass Separators

Price on Application

A Bypass Oil Separator is used in a ‘low risk’ environment where there is no requirement to provide full treatment for the flow; for example a car park where the risk of a significant spillage is small.

Designed and tested to BS EN858 parts 1&2, Marsh Hydroil bypass separators are manufactured from virgin unfilled resin offering exceptional durability, impact resistance and are guaranteed to be watertight and of uniform thickness. These combined properties ensure that the full range of separators stand up to the most rigorous conditions during their service life.

Internal working components, such as coalescing filters, weirs, oil skimmer plates, and their configurations offer the most modern and efficient oil/water separation capability available to the market today.

A wide choice of inlet and outlet positions are available on the units – detailed requirements should be provided at time of order (standard inlet and outlet positions will otherwise be fitted).

Typical applications

  • Car parks
  • Roadways
  • Industrial estates
  • SuDS
Product Details
Product Details



Product Code


Bypass SeparatorMarsh Hydroil bypass separators are designed to treat 10% of peak flow.

The drainage areas served by each separator are determined in accordance with both BS EN858 parts 1&2, but also with reference to a formula provided by the Environment Agency, where NSB=0.0018xA (catchment area in m2). Flows from higher rainfall rates are allowed to bypass the main separation chamber.


  1. Inlet
  2. Oil skimmer plate
  3. Coalescer
  4. Outlet
  5. Access turret
  6. Level alarm dip pipe
  7. Air vent