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PostPosted: Sep 25th, '12, 04:43 
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Hi!

Please forgive me if this is the wrong spot for this.

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This is our new setup and we are pretty excited! The bottom tub is 35 gallons.

Here is the trouble:

I've got a bell siphon in each corner. This is based on the UH bell siphon pdf document. The only exception is that I did NOT put the clear tube on that goes from the top of the "over tube" outside. The systems (both beds' siphons) work beautifully when I have the flow up high. When I turn it down to the correct setting, the siphons won't start.

So is the answer that little tube? I know folks run bell siphons without them. And I don't want to go to the drill-build-silicon effort if that isn't the problem.
Mahalo for your help! And, yes, I know the little pots on the right won't get much help in their current potted situation. They are resting. : )


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PostPosted: Sep 25th, '12, 15:18 
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The answer is that the pipe sizes you have used require a certain level of flow to work properly. I don't know that adding the breather hose will make much difference. Perhaps if you only use one siphon it might work, block the other one off and see how it goes. Ooops, I just noticed that it's two beds..

Take the bells off and make them constantly flooded beds... :)

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PostPosted: Sep 25th, '12, 15:32 
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I also built my siphon from the UH document. I originally added the breather tube and now have it tied off. It made no difference except for noise.

EB hit it on the head. It's all about flow rates (or rise rates, but that's splitting hairs) and pipe sizes. Too little flow and the siphons won't start. Too much and they won't stop.

You'll need to be able to regulate flow to each grow bed separately. You could start with ball valves on the output to each bed, but my head says that as you reduce flow to one side it will increase on the other. Not sure if that's true or not.

I'd also recommend looking into Affnan's style siphon. Adding a funnel to the top of the stand pipe will give you some flexibility on the flow.

Web4Deb has an interesting floaty cup breather design that could work if you have issues stopping the flow.




If you master the siphon, you're half way there.

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PostPosted: Sep 26th, '12, 02:56 
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So it sounds like the standpipe is too large a diameter, correct? That was my thought. Because, as I sat there observing my aquaponics (I think this is a formal activity :) ), I realized that if the pipe is large the water will just trickle in, not flooding the pipe to create the suction. So there is never a "wall of water" exiting the standpipe. My thought is if I neck down the standpipe to, say, 1/2", that it will "flood" more easily to create the initial "grab" needed to lock the suction in.

Tell me I'm crazy?

My thought is that I need to neck down the standpipe for a sufficient length to build up a little "pull."


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PostPosted: Sep 27th, '12, 00:12 
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Okay, Affran's looks like making the standpipe larger, but I have a hunch the large pipe is what is creating the issue. I also dig the "Better Bell," slowRider. I'm wondering if adding a trap to my drains could help?

I know a great deal of this is going to be cutting and rebuilding pvc, which is expensive. And I should get a pvc cutter. The chop saw is fast, but it is going to suck to get it in the growbed to mess with the standpipe. I kid!

Meh, what else am I going to spend my money on?


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PostPosted: Sep 28th, '12, 15:20 
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I tried adding a trap to my drain and wasn't able to get the siphon started. I have a feeling it was too large of a trap, but didn't try anything else. Theoretically, a trap should improve both starting and stopping. It does sound like your issue could be caused by a standpipe whose diameter is too large. The funnel would help that by increasing the volume of water that can pour in at once while not increasing the space required to create a seal (assuming he funnel was short enough)

You should be able to get the seal by adding the trap, but the dynamic changes significantly with a trap. With a straight drain, a vacuum is created in the bell and that eventually sucks more water in until you get critical mass and the siphon goes full bore. With a trap, you're creating pressure under the bell since the water under the bell has to push the water out of the trap to the point where a burp happens, then the pressure equalizes. After enough burps, all the air is gone and the next burp starts the siphon... or something like that ;) It works, but it works differently and I would think it would have to be troubleshot differently if things to awry.

If your issue is standpipe diameter, I'd try adding a choke point in the standpipe. Like, go from 1", reduce to 1/2", then back to 1". Since all you really need is a seal to start the siphon, that should give you what you need without purchasing much extra PVC or changing how it interfaces with your growbed


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PostPosted: Sep 28th, '12, 15:50 
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CageyMack: Just put a reducer on the end of the pipe where it drops into the fish tank. From the look of it in the photo I think you have too large a diameter pipe. Alternatively at the 90 deg bend in the drain, remove the pipe after the bend and twist the bend around so it points upwards at 45 deg.

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