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Mag Drive acting like a siphon?


RC1313

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Hi everyone, I was just installing my sump with a magdrive return. A 10 gallon was all I was allowed to have. Anyways, I was running some tests, and unplugged the pump to go eat dinner. Upon returning to my tank, there was about 10 gallons of water on the carpet. The pump was actually siphoning water out of the tank via the return jet down to the 10 gallon below. Has anyone else had this happen or know why it is happening?? Thanks

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Yep. If the return is below water level, it will back siphon until the return is no longer submerged. You either need a siphon break or move the return closer to the surface. The level you run the sump at should be able to accommodate the water that will back siphon with loss of power

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Yep. If the return is below water level, it will back siphon until the return is no longer submerged. You either need a siphon break or move the return closer to the surface. The level you run the sump at should be able to accommodate the water that will back siphon with loss of power

Yeah the problem is I'm limited to the 10 gallon. Thanks for the help.

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^That can still not be enough to stop a siphon.

 

Lift your return jets until they are just barely under water or even very slightly above. as soon as the pump turns off, water will reverse direction until the pipe is drained. A check valve often just slows it down.

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^That can still not be enough to stop a siphon.

 

Lift your return jets until they are just barely under water or even very slightly above. as soon as the pump turns off, water will reverse direction until the pipe is drained. A check valve often just slows it down.

Okay thank you. There is a ball valve (not ideal but thats all the store had).

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Do you want to shut that every time you turn off the pump? I know I'm lazy enough to not want to do that. :)

I originally had it there to slow the flow of the pump going into the tank so my eshopps overflow wouldn't be so loud. I'm probably more lazy than you..I'll move the jets up. Just had no idea that the pump did that :happy:

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It's not the pump, it's gravity and how siphons work.

 

If you had no pump there, but filled the line with water, it would pull water out of the tank until air entered the line. Even if that means going uphill on the way and/or overflowing the sump. Don't quote me on this, but I think it's just surface tension that holds it together, even uphill.

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It's not the pump, it's gravity and how siphons work.

 

If you had no pump there, but filled the line with water, it would pull water out of the tank until air entered the line. Even if that means going uphill on the way and/or overflowing the sump. Don't quote me on this, but I think it's just surface tension that holds it together, even uphill.

I'm an idiot and didn't realize the pump made a siphon I guess haha. I think it might be called cohesion or something. Thanks for the help again

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It's not the pump. It's the return line. The pump doesn't cause the siphon, the siphon just happens when the pump isn't running to prevent it.

:lol:

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It's not the pump. It's the return line. The pump doesn't cause the siphon, the siphon just happens when the pump isn't running to prevent it.

:lol:

:slap: :slap: Me over and over again

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1) drill a siphon break, 1/8" or smaller hole as high on the return piping as possible

2) add check valve, test and clean it regularly

3) sump design shoul be large enough to handle siphon back flow

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