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Old 03-06-2009, 09:07 PM   #11
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I imagine that the box will have teeth on it. Pretty standard I think. 6x6x6 kind.

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Old 03-06-2009, 09:27 PM   #12
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Originally Posted by Reefer27 View Post
I don't see the need for a drilled return line. I don't mind piping over the back of the tank. Plus this way there is no siphoning chance. ( I know not much would siphon back).
If your return line is underwater, no matter if it's over the top or thru a hole, the water will siphon back into the sump until the water level in the tank drops below the level of the return. You can go over the back, but if you take the return line to the bottom of the tank, when the pump is off the entire tank will drain. If it's 4" deep, it will drain 4" of water.
You can take the return all the way to the bottom or as deep as you want, IF you drill a small hole in the return line near the surface (1-2" deep), so when the water drops it will break the siphon. Basically, it doesn't matter if it's drilled or over the top if you set it up correctly to break the siphon before the sump floods.

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Old 03-06-2009, 10:01 PM   #13
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Thanks ccCapt. Good point. I imagine most return lines are underwater? Where exactly do you drill the hole. I understand the concept and it makes perfect sense. You mention 1" to 2" below the surface. (Or whatever level that your sump has capacity for in case of a power outrage?)

Just having a hard time picturing. So if the return line went over the back and straight down the hole drilled would be facing you as you look at the tank?
A pic would be great.

And how big is the hole? What size drill bit?
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Old 03-15-2009, 08:21 PM   #14
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It doesn't make any difference which way the hole faces. The purpose is just to let air in to break the siphon when the pump loses power. Size matters a little, in that it needs to be big enough to let air in fast enough that an air bubble forms at the top of the pipe rather than smaller bubbles being entrained in the siphon flow and swept down into the sump. No size is really too big though, except that it will redirect a portion of the flow. That may or may not be a problem, depending on application. Minimum size would be easy to determine experimentally. Just start with a small one, run the pump and turn it off, then watch if the siphon is able to draw water out of the tank below the level of the hole.

Typically you want the return line underwater to minimize splashing noise, and also if you want to create current in the tank it makes it easier to direct the outflow.
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Old 04-21-2009, 03:54 PM   #15
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a flap check valve would prevent any backflow and doesn't burden the pump. Best way to prevent a flood from backflow siphoning.

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