Auto Bell Siphons are ingenious devices and have been the standard way of generating the Ebb-and-Flow cycles in small/medium media based aquaponic systems for decades. They are cheap and quite reliable.
Although they do have some drawbacks:
1- They can be quite tricky to set up as they require to be precisely engineered and carefully adjusted to work on a specific system (e.g flow rate. pipe length, hydraulic characteristics the grow-bed)
2- There is no control over ebb-and-flow frequency, neither an quick way to adjust the water level in the grow-bed
      Our first client and long time partner Incredible AquaGarden based in Todmorden, UK was facing this challenges when we were hired to consult in their system construction. They have a quite unusual and challenging media based grow-bed with it’s 10 meters long. We set the goal to solve this problem and improve in their system operation. Our open source ethos and the desire to make an affordable solution lead us to join forces with the FabLab Manchester to develop an practical and affordable solution.
      The first version of the valve was 85 cm long and cost £70 in material (while an electronically actuated valve with similar functionality would cost £300 – 500). It was an air actuated water valve built using material sourced from local hardware shop (piping components), a bike inner tube and commodity electronics components (e.g. Arduino and Raspberry Pi)
     

                                                                                                                                         

Version 1 at Incredible AquaGarden


       The valve performed it’s work well for almost two years without any mechanical problems, although issues with the electronics controllers and software maintenance required an upgrade to new version with a stand-alone controller based on a new chip-set (ESP 8266)
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Close up of Valve

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Version 2 at Incredible AquaGarden

Stand-alone Grow-bed controller

Stand-alone Grow-bed controller

 

      Further developments have lead to an fully integrated and compact device built using off-the-shelf components and a 3D printed part, with material costs (labor not included) around £15
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Version 3

      Our valve enables to easily customize the water level in your grow-bed. It’s a more adjustable alternative to Auto Bell Siphons and it works straight out of the box:
 
-If days are warmer and/or the plants are younger you can decide if you want the top layer of the grow-bed wetter therefore providing a better environment for the new seedlings.
 
-There is low risk of clogs as the shutting mechanism works by pneumatic compression of an elastic tube (bike inner tube – butyl rubber)
 
-During the night the ebb-and-flow cycle can be interrupted to enhance the bed (i.e plants and microorganisms) access oxygen to and to facilitate earth-worms to travel through it.

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