Backyard Aquaponics
A place to discuss aquaponics

I'm having trouble stopping the siphon effect. I have 4 - 4'x4'x12" IBC grow beds and I built a bell siphon (1" standpipe, 2" bell siphon with cap, uniseal, 7/16 OD, 5/16 ID snorkel tube) for each one using U of Hawaii specs (link below). They worked perfectly without any grow media (graVEL) in the grow beds, good consistent flood and drain on each one. I added the gravel and the siphon still triggers but will NEVER stop. The snorkel tube never seems to get enough air to stop the siphon. I've troubleshot over and over and cannot correct it. I've adjusted the flow rate, retied the snorkels to be certain they werent being constricted, cut the snorkels back, made teeth on siphon bigger and smaller, removed uniseal from connection in drain pipe, drilled more holes in 4" screen guard, etc. I've include several pics hoping someone can see an obvious problem I'm simply overlooking. Any suggestions/alternatives. I appreciate the help, I'm so close to planting. Thanks

U of Hawaii bell siphon http://www.ctahr.hawaii.edu/oc/freepubs/pdf/BIO-10.pdf

More photos part 2

more photos part 3

more photos part 4

last photo
Thanks for the help

I think the problem is that the drain from your siphon is not long enough.

Check out this thread:

viewtopic.php?f=18&t=12426&hilit=physics+bell+siphon

Couple of things:
1. Get rid of plastic tube on the bell. Not necessary.

2. In photo 5, the angle of the pipe looks like it is running uphill. This will allow water to be trapped and prevent air coming back up the drain. Lower the outlet of the pipe.

If the siphons started/stopped fine with only water in the GB's, but won't stop since you added gravel to the GB's, and you didn't change anything else... then it must be a flow problem.

I know you say you've tried adjusting the flow, but how far?... it takes a lot less flow to get the siphons working in a GB containing gravel, compared to one with no gravel.

Having a siphon that won't stop is normally easy to resolve...

1. Grab a beer and a chair, park yourself in front of your system.
2. Turn the GB in-flow tap down just a smidge.
3. Wait a couple of minutes to see if the siphon stops.
4. If it doesn't stop... repeat steps 3 and 4 until it does.

+1 on the pipes under the beds running uphill. Siphons will not stop with that happening. I found this out when one of my beds sunk a bit

My bad... step 4. should've read: "If it doesn't stop... repeat steps 2 and 3 until it does.


N.B. The first part of step 1: ... can be repeated as often as desired/required

I like Mr Damage's steps - specially step 1. I think almost everything AP should begin with that step 1 (note: when building your system - that should be the last step, not the first step).

@Ragin' Cajun

I would follow Mr Damage's steps but would also look at the return pipe. It may be better to use a 90mm T piece and have your standpipe discharge into that rather than directly into the return pipe with a uniseal as this is a place which air may come from to break the siphon.

Removing the uniseals from where the siphon outlets meet the 3" pipe under the growbeds (photo_5) might help.. The siphons break by letting air in but they need to get air from both ends..
The outlets running uphill may also be what's stopping the air, but taking the seals out might lower the pipe enough too..

Tanks for the thread. Not to debate you but why would the siphon trigger and break properly before grow media added with same length of drain from syphon? Thanks

Thanks for the response. Thought that the plastic snorkel tube on the bell was to help and/or break siphon? I'm going to angle the pipe downhill to see if that corrects it, thanks.

I like your idea about the chair and a beer. May substitute beer with vodka. Thanks for tip, I may have to insert some flow regulators to slow the water coming in.