Anti syphon holes

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jim barry

Goliath Tigerfish
MFK Member
Jun 21, 2006
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Hi all

Where do I drill anti syphon holes so the back syphon to the sump is broken when the return pump stops for any reason?
Do I drill the anti syphon hole below or above the water level?
 
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Hi all

Where do I drill anti syphon holes so the back syphon to the sump is broken when the return pump stops for any reason?
Do I drill the anti syphon hole below or above the water level?

I've seen it done both ways.

You can drill it just below the water line as mentioned, and then when the water level drops to the level of your hole it starts sucking air and the syphon breaks. The slight disadvantage of this is that you have 'x' amount of water back syphoning down to your sump until that hole level is reached. If you've plenty of room in your sump, great.

For an even quicker break you can drill the syphon slightly ABOVE the water line and then the syphon will be broken very quickly because it starts sucking air instantaneously. Though, if you do it this way make sure the small syphon hole you drill is facing towards the surface of the display tank, otherwise when your pump is running you'll have a jet of water spraying all over your canopy or floor!! And depending what your turnover rate is, this small jet of water hitting the surface may be slightly audible.
 
jim barry jim barry fumny I just brought this up on your other thread. I didn’t see this one.
Just disregard.
The hole will actually set the water level so drill it where you want that level to be.
 
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jim barry jim barry fumny I just brought this up on your other thread. I didn’t see this one.
Just disregard.
The hole will actually set the water level so drill it where you want that level to be.
My mistake.
I missed the “back siphon “ part. In my mind I was thinking it was the drain side.
 
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