A Community and Forum For Aquaponic Gardeners

bell siphon

im having trouble with my siphon i have a 20 gallon fish tank and 15 qrt grow bed i know its small im just starting out i also have a 80 gph pump that pumps water the my bed i have a 3/4 in stand pip for my siphon is that to big for my 15qrt grow bed because for some reason it dont kick in just trickels out thanks for any help

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Permalink Reply by Kobus Jooste on March 7, 2011 at 6:56am

The pipe diameter could be a bit thick, but I have found that for me, the outflow configuration has a greater role to play than the diameter of the pipe alone. What I have done in the past is to put the water pipe draining the bed through at least one 90 degree bend and a piece of horizontal pipe before dropping it back into the fish tank. I have also hear of people using plumbing style s- or u-bends to retard the flow of the water between the outflow and the fish tank. The idea is to slow the flow of the water sufficiently to allow the stand pipe to fill, thereby activating the siphon. For a number of reasons, if the flow is too fast or too slow, the siphon will not kick in or stop flowing - your comment makes it sound as if it does not want to start, which leads me to make the initial suggestion above. Let me know if this helps or not.

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Permalink Reply by TCLynx on March 7, 2011 at 8:35am

If a siphon just trickles over but doesn't kick in, then the siphon is either too big or the inflow to slow.

If a siphon kicks in but won't stop then the siphon is too small or the inflow too fast.

There are tricks that can help get the balance right. Like as Kobus says adding some elbows at the bottom since sometimes a bit of a trap at the bottom will keep it from trickling over until there is enough pressure to push the air bubble past the trap and get the siphon properly kicked in, however this often stops the siphon from getting a good gulp of air at the end and stopping properly so people often have to add a breather tube as well.

So another option is to look into the Affnan modification to the bell siphon to help it operate with a wider range of flow rates. Here is a link to his blog that may provide some help. Affnan