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  1. #1
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    Drilling an hole in the return pipe to break the syphon

    Hi everyone,

    Is there a tips how to avoid bubles in water if you drill an hole in your return pipe to avoid a flood caused by the syphon effect of the return pipe ??

    Steve

  2. #2
    Senior Member colesy's Avatar
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    I am probably just being dumb, but how could you drill a hole in your return pipe without the water coming out of that hole?

  3. #3
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    The syphon break hole is often placed just under the surface of the water. That way, if power goes out, there will be some water leave the display tank but when the hole gets above the water level, the syphon is broken.

    Zeke, are you having trouble with bubbles? Or is this more of a theoretical question? I get no bubbles from my anti-syphon hole.
    Nick

  4. #4
    Moderator cres's Avatar
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    Actually, because of the Bernoulli effect, water or air will be drawn in the hole as the return water flows past. Since somewhere between 1/4" and 1" of water will drain due to the overflow anyway, creating the syphon break hole or holes just under the water level is fine.

    Personally, I use both a syphon break hole and a check valve. I found that a 1" PVC pipe required a fair amount of syphon break. A single 1/4" hole simply drew air in which wasn't quite enough to break the syphon quickly. With the check valve at least slowing it down (or preferably stopping the flow), the syphon break hole didn't need to be quite as big.

    EDIT
    If you use a penductor/eductor, there will be pressure in the return line, even below the water line, and you should expect water to flow out of your syphon break holes.
    Sarchasm: The gulf between the author of sarcastic wit and the person who doesn't get it.

  5. #5
    Senior Member Chrispol's Avatar
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    what i did was drill a hole glue in a nipple, and run airline to my overflow so it was allways exposed to air, i find with a higher pressure pump if you drill near the surface intank you get a weird high flow hole sometimes
    675 Gallon Aquarium in the works

  6. #6
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    I will go to bed less dumd tonight !!!! :speedbana

    These are all great ideas...

    This is half a theorical and half practical question!

    I am starting to do some test and final ajustment on my new setup and I have some buble in the main tank and a big part of it is due to the holes I drilled to break the syphon.

    I will try one or more of your ideas guys !!

    Thanx again!!

    Steve

  7. #7
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    An elevated "loop" on the return line is also a very good idea and will add only about 1 foot of head.
    Rob

  8. #8
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    what exactly do you mean by an elevated loop on the return line?

  9. #9
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    An elevated loop is an extra foot of return hose that is ABOVE the tanks high water line. It is formed into a circle above the tank so that a back siphon is unlikely to occur. It is difficult for a gravity activated siphon to draw water upward through the loop. It is similar to a drip loop that is often recommended on power supply wiring.
    Rob

  10. #10
    Junior Member
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    Quote Originally Posted by cres
    Actually, because of the Bernoulli effect, water or air will be drawn in the hole as the return water flows past. Since somewhere between 1/4" and 1" of water will drain due to the overflow anyway, creating the syphon break hole or holes just under the water level is fine.

    Personally, I use both a syphon break hole and a check valve. I found that a 1" PVC pipe required a fair amount of syphon break. A single 1/4" hole simply drew air in which wasn't quite enough to break the syphon quickly. With the check valve at least slowing it down (or preferably stopping the flow), the syphon break hole didn't need to be quite as big.

    EDIT
    If you use a penductor/eductor, there will be pressure in the return line, even below the water line, and you should expect water to flow out of your syphon break holes.
    Great advice. Question though. I was thinking of doing a check valve myself however,does the valve itself act as a restriction to passing water at all?

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