# Can I cover the anti Siphon hole in a return line?



## twobytwo (Oct 25, 2014)

The drain in my overflow has a higher flow than my return. No big deal right? "Better than higher flow on your return!" - I agree

However, when the water level in the overflow dips a bit below the return standpipe, water under pressure comes out the pre-drilled "anti-siphon" hole. And it makes noise. If I cover the hole with my finger, no more noise.

The loc-line splits and there are 2 nozzles for the return water. If I have at least one nozzle just at the water line in my DT, can I cover the little hole in the return? My sump capacity of about 40g is only about 3/5 full so in a return pump failure, the water siphoned back shouldn't be enough to fill the sump.

Based on these conditions, can I cover the hole in my return and make my system quiet?

Pic of return from the side:


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## sig (Dec 13, 2010)

can we see complete picture of your durso? why you really care about siphon from the return?
keep the outputs of the return not below teethes of overflow and never worry

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## twobytwo (Oct 25, 2014)

sig said:


> why you really care about siphon from the return?
> keep the outputs of the return not below teethes of overflow and never worry


I don't care about the Siphon, per se... I care about the noise from the water rushing out.

After I cover the hole, can I just keep one output above teeth or do both need to be above?

under water:









Above water:









Ignore the foam at the return. After a suggestion from someone on the board, I just wanted to seal up the opening so fish can't wander into the overflow box.


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## J_T (Mar 25, 2011)

Cover it, and turn off the power...

See what happens in a controlled situation.


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## sig (Dec 13, 2010)

twobytwo said:


> I don't care about the Siphon, per se... I care about the noise from the water rushing out.
> 
> After I cover the hole, can I just keep one output above teeth or do both need to be above?
> 
> ...


I would not have output so low

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## reefgeek (Dec 31, 2014)

Instead of covering the hole, insert a piece of RO tubing into the hole, deflect it downwards to just above or below the waterlevel. Did this with mine and have no sound, the second the power is cut the line draws air and cuts the siphon.
I had to silicone the RO tubing in place as the pressure was pushing it out from time to time.


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## fesso clown (Nov 15, 2011)

Looks like the top nozzel of your split locline is high enough. The syphon will break as soon as air enters one of the nozzels. I don't have a hole drilled at all, I just have one of my loc-line nozzels close to the surface so that not too much water drains before air is introduced. 
But yes, do what JT said and test it and see how full your sump gets.


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## sig (Dec 13, 2010)

fesso clown said:


> Looks like the top nozzel of your split locline is high enough. The syphon will break as soon as air enters one of the nozzels. I don't have a hole drilled at all, I just have one of my loc-line nozzels close to the surface so that not too much water drains before air is introduced.
> But yes, do what JT said and test it and see how full your sump gets.


good point. never was thinking about it 

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## twobytwo (Oct 25, 2014)

Thanks guys! Got home, covered the hole with electrical tape and then shut off the return pump. Overflow drained to the holes in my... drain. DT level went down for a moment until - as expected - air entered the loc line, and then everything stopped. I still have room for another 10 or so gallons in the sump for a catastrophic emergency, but looks like I won't have to worry.

I also turned the top nozzle so its vertical like the other one and would pull in air a little earlier.

Picked up some cyano glue from the dollar store, will plug the hole tonight.


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