This siphon evolve from the classic "Loop Over The Barrel" siphon. Its made up of a flexible tube, with fittings to accomodate the water drain to tube routing.
Diagram above shows the siphon construction.
Siphon action occur as soon as the water in growth bed reaches the "High Water Level" and as the water flow through the loop, siphon action started.
Diagram above shows, water reaches the lower limit, of the growth bed, at this point the water will cut off due to air will start to flow in the tube.
This siphon is very simple in construction, however it is difficult to get it "just right" for siphon top occur and cut-off.
Pump pressure decay, will cause siphon not to occur and if too much pressure, siphon may not stop.
This siphon suffer same problem as the straight stand pipe Bell Siphon.
Loop Siphon - Internal
This is the loop siphon install inside the growth bed. The water outlet can be at the bottom (as shown) of at the side of the growth bed.
Swivel Valve Siphon (Loop Siphon Modified)
This is the loop siphon, with venturi adapter to ensure better outflow
Diagram above shows construction of the swivel siphon.
Siphon action start, as soon as water reach high level of the growth bed, just like normal loop siphon.
The siphon is made to swivel at the attachment "Tee" making possible to change water level while maintaining constant size of the siphon.
Loop siphon made from tube may deform as the loop adjusted for water height, thus making it difficult to get it right.
Water reaches low level, hence stopping the siphon.