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  1. #1
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    Bell Siphon issues

    Forgive me if this has already been coverd 10000 times, but I cannot seem to keep my bell siphons from running continuously. When the siphon starts, you can see the water level drop rapidly, however, once it gets to the air holes it just gurgles and the siphon will not break.
    I know this is not the issue.
    1. the height of the stand pipe cap. tried caping just above the stand pipe, and have also left a 3" cap between top of stand pipe and cap. Doesnt matter.

    2. the diameter of the stand pipe. I have used 1/2"PVC and 3/4" pVC. Each diameter will drain the bed faster that it is being filled.

    The only thing I havent tried is to put and reducer(on inducer hower you look at it.) on the stand pipe to create the venturi effect per Annan's videos on youtube.

    Suggestions?

  2. #2
    Moderator urbanfarmer's Avatar
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    Re: Bell Siphon issues

    Reduce your flow into the grow bed and see what happens.

    Try a bigger air pipe to break the siphon or did you not use one at all?

    Change the configuration of how the pipes that exit the siphon are. Remove everything so it just "drops" straight down. Do you have elbow fittings?

    A picture would help us help you. There are so many ways to mess it up I can't just magically give you an answer based on that little information. Thanks!

  3. #3
    Moderator davidstcldfl's Avatar
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    Re: Bell Siphon issues

    EDIT: Opps....didn't see UF's post...still working on my coffee.

    Hi flienlow, If your bell siphon doesn't stop draining, it could be, something as simple as the water comming 'in', is too fast. You could split the line coming to the media bed, and send some back to the fish tank. Which could help add some oxygen.
    You mentioned, adding a reducer to the stand pipe (affnan style). Normally this helps to 'start' the siphon. From experience, I noticed, that this speeds up the 'draining' of the media bed. The extra speed, 'might' help break the siphon.
    The other option, is to try adding a snorkel tube. It's just a small tube, that comes out of the side of the 'cap'. How far it goes towards the bottom of the bed, sets where the siphon breaks. Here's a pdf, that explains their use...
    http://www.ctahr.hawaii.edu/oc/freepubs/pdf/BIO-10.pdf

    Sorry, I was confused by what you described in #1....?
    Quote Originally Posted by flienlow
    1. the height of the stand pipe cap. tried capping just above the stand pipe, and have also left a 3" cap between top of stand pipe and cap. Doesnt matter.
    I'll just mention some stuff, which sounds like, you've already done or know....?
    -If your using a 3/4 inch 'stand pipe', your 'cap pipe', should be twice the size, or 1 1/2 inch.
    -The 'outside' bottom of the 'cap' should be at the height of the 'stand pipe'.

    Good Luck ...
    "Freedom is never more than one generation away from extinction. We didn't pass it to our children in the bloodstream. It must be fought for, protected, and handed on for them to do the same." - President Ronald Reagan

  4. #4
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    Re: Bell Siphon issues

    my stand pipe is 3/4" and the cap pipe is 1 1/2". I also have a 2" strainer pipe that surrounds that with 1/8" holes throughout to keep the hydroton out.
    The drain from the grow bed is 3/4" (it is necked down to 1/2" as I am using a 3/4" bung fitting through the grow bed, but that is just a pvc adapter to thread into the bung fitting and accecpt 3/4 pipe.) The 3/4" drain goes down and hits a 90 (possible issue?) and then travels to a 2 1/2" "T". I am using the "T" with about 6 inches of 2 1/2" pipe on either side with holes drilled in it. The thought behind that was aeration for the fish, and not wanting to blash them with a 3/4" drain flow.

    here is a picture of my system.
    No Fun with Hydroton

    The 3 orange home depot buckets have been replaced with 1 large grow tray.
    Possible fixes:
    1. get rid of 90 degree (would need new diffuser solution)
    2. 400 Gal/hour pump too much? divert some water back to fish tank with a aerator from fill?
    3. investigate "tube" on cap pipe
    4. inducer on standpipe.

    This is the best I can come up with on your suggestions.
    Thank you all

  5. #5
    Members bsfman's Avatar
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    Re: Bell Siphon issues

    I'm no expert on bell siphons, but before doing any major drain reconfiguration or changing your pump input rate, you might try increasing the hole size at the bottom of your cover pipe so as to allow a bit more room to let air in to break the siphon at the end of the cycle. If that doesn't fix it, then you could try the more labor intensive suggestions.

  6. #6
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    Re: Bell Siphon issues

    from my experience, the hole size doest matter. The water dips to a certain level and stays there. I have 4- 3/4" holes on the cap pipe. More than enough.

    But thank you for sharing!

  7. #7
    Moderator urbanfarmer's Avatar
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    Re: Bell Siphon issues

    Quote Originally Posted by flienlow
    from my experience, the hole size doest matter. The water dips to a certain level and stays there. I have 4- 3/4" holes on the cap pipe. More than enough.

    But thank you for sharing!
    Of course it matters! Where the air holes are in relation to each other can have an effect too. Ideally, you want it configured in such a way that the maximum air gets introduced into the pipe at one time otherwise the force of the vacuum will pull more water and continue the siphon (not what you want). YouTube fluid mechanics. There are a lot of basic conceptual videos that will give you an idea of what you're doing.

    I can't really see the bell siphon from your picture, but it looks like you have several feet of pipe after the bell siphon... LOL! Even if the siphon gets air in the force of the water siphon in the rest of the tube will keep the siphon going. That means the water flow is about right for this condition. You probably hear a "gurgle gurgle gurgle" sound but it keeps on truckin' right?

    Get a better picture of your siphon. It's impossible to guess what you did based on your description. You probably want a T fitting near the top of that long tube so that it doesn't make a siphon, but even then you will have some force from the resulting pressure differences.

    Good luck!

  8. #8
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    Re: Bell Siphon issues

    Quote Originally Posted by urbanfarmer

    I can't really see the bell siphon from your picture, but it looks like you have several feet of pipe after the bell siphon... LOL!

    Even if the siphon gets air in the force of the water siphon in the rest of the tube will keep the siphon going. That means the water flow is about right for this condition. Hummm...... I have seen videos where there have been long pipes after the siphon but they still stopped?

    You probably hear a "gurgle gurgle gurgle" sound but it keeps on truckin' right? YEP! How'd you guess?

    Good luck!
    At any rate a picture is worth a 1000 words and I need to provide photos. I wonder if I need a larger diameter pipe after the siphon that will introduce more air, perhaps venting the drain pipe somehow, or maybe just getting rid of the elbow will do it. The force of the water comment made me think. Fluid dynamics is getting the best of me.

    Thank you.

  9. #9
    Moderator urbanfarmer's Avatar
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    Re: Bell Siphon issues

    Well, if that 3-4 foot pipe is connected to the bottom of the siphon without breaking the siphon when it first comes out, then the WHOLE PIPE is part of the siphon... and unless you designed it that way for a reason, that in itself will create problems... it's easily fixed, but IDK if that's what's going on or not... we'll wait for the pics

  10. #10
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    Re: Bell Siphon issues

    If the siphon won't stop it is like UF said. The air tube that goes from the top of the bell to the point you want it to stop is plugged up. Make sure it is clear. Once air is introduced at the top of the bell, it will stop. The tube need not be big. Mine are only 1/4" OD aquarium tubing and my bell is a 2" pipe and the stand pipe is 1". Here are some shots of mine:



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