Breaking a return siphon

[inktomi]

Hello folks...

First, let me appologize about even posting this thread. I know I'm supposed to drill a hole to break the siphon, and I know that hole should be just under the water level when the tank is running.

The issue is - I drilled the holes in my return pipes just below the normal water level. This is inside the overflow in the back of my tank. When I unplug the return pump, these do not break the siphon - because there's no siphon to break. Water shoots out of the holes, and continues to drain down into my sump.

What should I change here? I get the whole water will find it's own level thing - in retrospect I'm not sure what I thought these holes would do since they're still below the level of the bulkhead inside the display tank. I even tried drilling a hole on the top of the elbow that goes into the bulkhead into the main part of the tank - now I just get a funny little spout of water there with the pump on, and a lesser spout when the pump is off and the sump is backfilling.

Help? I'm not sure what to do.

Here's a photo of the elbows before I tried to drill the siphon break.

<a href="http://www.flickr.com/photos/30998766@N03/3760471576/" title="Overflow by inktomi, on Flickr"><img src="http://farm3.static.flickr.com/2675/3760471576_7313478ff7.jpg" width="500" height="334" alt="Overflow" /></a>

I drilled holes into the two 3/4" elbows trying to get the siphon to stop. I think I need to go to Lowe's tomorrow and get fresh elbows now =p :rollface:

Obviously the issue is that the "normal water level" in the overflow is still below the normal water level in the display - so no amount of holes in the return plumbing in the overflow is going to stop the siphon..... but there has to be something I can do!

 

[steve70]

you do that on your return line, not your overflow.

 

[inktomi]

So I should be drilling the holes on the locline or whatever I put on the inside of the tank?

 

[Steve175]

You're stuck with whatever is draining from the overflow during a pump failure. The siphon break is for the returns so that they don't suck additional water from the main tank back into the sump and contribute to a possible flood from the sump (and resultant divorce). HTH

 

[wrott]

Or just point the outlet up, just below the waterline so that it starts drawing air almost imediately after pump is off.
This is the only way to be sure to stop a siphon.

 

[inktomi]

Hmm that's a good idea. I could get an eblow that's 3/4 male slip on one side, and maybe 1 or 2" on the other, and point it up - the size change would prevent me from spraying water onto the ceiling.

I'll try that if the locline idea doesn't work. I'm going to install two sets of locline and create an upward bulge in the middle so that water would need to go up a hill in order to back siphon - then I'll drill a small hole just below the water on each locline set.

 

[Agu]

The issue is - I drilled the holes in my return pipes just below the normal water level. This is inside the overflow in the back of my tank. When I unplug the return pump, these do not break the siphon - because there's no siphon to break. Water shoots out of the holes, and continues to drain down into my sump

I suspect your siphon break isn't working because you're on the "downhill" side of the flow. It can't suck air because it's full of water. Replace the elbows, add a piece of pvc that extends past the edge of the overflow and add a 45 elbow to connect your locline to. Angle the 45 down a little bit. Drill the siphon break in the bottom of the 45.

Or just make sure the locline outlet is close to the surface so you don't need a siphon break. The hump you mentioned will do nothing to prevent backsiphoning.

 

[inktomi]

That's a good idea with the locline spout being near the top of the water. That would work well, and help push around the stuff that floats up on the top of the water. I'll probably just have the output from the locline be at the surface - it solves two problems at once.

 

[reefworm]

just for insurance, drill two holes in case one gets crudded up or plugged by a snail - you never know...

 

[inktomi]

Will do. How large would you say to go? 1/4"? 1/8"?

I'll be using 3/4" locline.

 

[reefworm]

1/8" should be fine