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FFI Siphon Fish Passes

A Unique Concept


  • All-species fish passage
  • Huge cost savings on new builds
  • Easy maintenance
  • Low visual impact on the surrounding environment


FFI Siphon Fish passes are a unique concept bringing two tried and tested systems together to provide the ultimate in fish passage technology.


Traditionally, pool and traverse fish passes are used mainly by larger, more athletic species. With a siphon fish pass, the flow rate through the pass can be controlled by incorporating this type of pass into a tubular siphon. Therefore, allowing the targeting of smaller species. Salmonid migration can easily be handled by the FFI Siphon Fish passes. To allow smaller species to pass in the offseason the siphon can be slowed down. Thus, allowing even frogs and elvers to use the pass. Elver substrate can also be fitted inside the pass to aid eel passage.


The FFI Siphon Fish pass is robust and easy to transport and install. Due to being manufactured using pre-fabricated lengths of Vinyl-Ester pipe. The installation typically requires the excavation of a trench. Then allowing the pass to be laid prior to being backfilling, similar to the installation of a common pipeline. Usually, there is no requirement for any foundation. Some installations requiring only a period of days rather than weeks. Complicated concrete works can be avoided. Therefore, the build cost is often far lower.


As standard, the pass incorporates a number of viewing windows to allow inspection. To flush the siphon and clean debris a set of sluice paddles in the base of each baffle can be opened in a single action. Other than occasional visual inspection and flushing, the pass requires very little attention.  Due to the high-quality materials used there is an exceptional life expectancy.



Low impact on the environment


The majority of the siphon can be buried underground. Only the viewing windows requiring access. The design allows for routing the pass around obstructions and also colouring to suit the surrounding environment.


A small vacuum pump is used to control the FFI Siphon Fish pass. This “tops up” the vacuum in the siphon as water carrying air reduces the siphoning effect. The vacuum pump operates automatically using a very small amount of power. This is often coupled with a small solar panel.


ACE also offers a range of fabricated fish and eel solutions for existing structures:


  • HDPE Larinier tiles, quick and easy to install
  • Fabricated Larinier Passes, custom built
  • Modular Eel passes
  • Special fabrications, including Alaskan “A” and Denile fish passes


For information on our recent fish pass installations, please see our case studies or contact us to discuss your requirements.



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