# Sump Return Pump - Reverse Siphon



## RRasco (Aug 31, 2006)

I built a sump for my 110g, when I unplug the return pump (to simulate a power outage) I get a reverse siphon back into the sump. I drilled a hole just below the water level to break the siphon and while it works to an extent, there is still a small siphon carrying water back to my sump. I don't see any water coming out of the siphon break though. I will modify the return outlet (a spray bar I built) to be higher if I have to, but shouldn't the drilled hole be enough?


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## mightyevil (Oct 23, 2008)

yes, the hole should be enough but the hole should also be big enough and should be drilled just above the water line not under it because the tank will drain water above the hole until that hole is above the water line. The bigger the hole the faster the siphon breaks.


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## fox (Jun 11, 2009)

No no no. The hole goes just below the water line. Don't go too low but just under the normal operating level.

Sometimes you will need to clear this of algae. It will be under pressure when the pump is operating then when if it powers down this algae could get pulled back in or a snail might plug it.

Since this is newly set up we can discredit that and assume the anti siphon hole might be a tad too small. What diameter drill did you use.


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## mightyevil (Oct 23, 2008)

Well, I guess it doesn't matter where the whole is but think about it, if you have it under water then the water level will drop until it reaches the hole, meaning the water will siphon back into the sump. If you have it above water it doesn't affect anything because it is an *output* but in case of the power going it there can be no water siphoning back except what there is in the tube/return traveling up.

I would only drill a hole under water level for an siphon *intake* so the siphon breaks as soon as possible.


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## RRasco (Aug 31, 2006)

I believe I used a 9/64 drill bit. I did make the hole smaller initially and tried upping the size already, which is why it is at 9/64 now, but same problem. Maybe I should go bigger? The bigger the hole, the more surface agitation and splashing that may occur, which is what I am trying to avoid. The PVC used for the return is 3/4".

It shouldn't matter where the hole is, but above the water line it shoots across my tank and splashes, it's a 600GPH pump. Under the water line it slightly creates surface agitation, which is what you see in the picture. That picture was with the smaller siphon break too. I know it will reverse siphon until the water level reaches the hole, which is when the siphon should break, in this case, it partially breaks. I wasn't sure if it was because the hole was too small or I was doing something wrong. I made sure the hole was high enough to break the siphon far before my sump is full, I have about 10 gallons before the sump overflows. It does happen though, I did it yesterday before I knew about the reverse siphon.


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## RRasco (Aug 31, 2006)

A better shot of the siphon break.


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## fox (Jun 11, 2009)

I think I used a 3/16 or 7/32 bit for the antisiphon break. Mine disrurbs the surface a tad. When I drilled it I purposely drilled on a very slight angle so it would point downwards.

mightyevil the tank is going to siphon back into the sump to the lowest *A*nti*S*iphon *B*reak. If you place the output ASB above the waterline you will still have the intake drain back to the sump until it breaks the ASB. The tank will drain below the normal operating level no matter what so why have the out put break siphon first and have to listen to it always splashing during normal operation if when the power goes out it is going to drain to the lowest ASB anyways?

I use durso standpipes mebbe HOB overflows work different.


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## RRasco (Aug 31, 2006)

@fox, so the reverse siphon will continue until it hits the LOWEST opening? Which in my case would be the spray bar outlets?


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## fox (Jun 11, 2009)

Okay I guess I should have said the lowest ASB of the intake or outflow. Sorry I should have been more clear 

My outflow breaks siphon before the drains so the tank continues to siphon down until the drain siphon breaks flow.

I use loc line for the outflows and they point downward lower than their ASB and it does not drain to the level of their tips.

Having only used durso standpipes I can not comment on how low a HOB overflow will siphon but I would still suggest to keep the outflow ASB just below the waterline to keep unessecary splash noise to a minimum and leave a gallon or three room in the sump for this. :thumb:


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## mightyevil (Oct 23, 2008)

I did not realize that there was so much water going through one return.

You need to treat the intake and output as different issues. We also need to know how the water is getting to your sump, what is your form of intake? Overflow box with durso pipe/regular pipes? Do you have a siphon type overflow? Do you have a pvc overflow?

You need to have the hole just above or just below your water line for your output (in your case just below because of all the water pressure going through 3/4" pipe). This will break the reverse siphon and stop water from going back into the sump as far as the output goes.

Whatever your overflow intake is like, it will draw water to your sump to a certain point. For Durso pipes and regular pipes it depends on how low your pipes are and actual overflow. The tank will drain until there is no more water going into your overflow box and until there is no more water going into the pipes from the overflow box.

I hope that made sense.


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## RRasco (Aug 31, 2006)

I am using a HOB with a U-tube siphon for my intake. I built the HOB to house a durso standpipe, but I am not getting enough flow from it so I am using an open 1" PVC drain pipe into my bulkhead until I can get the durso pipe calibrated. I would remove the PVC altogether, but I need the water height to remain high to maintain a siphon in the U-tube. The inside intake box is small, so the overflow stops pretty quickly after I cut power to the return pump. I will post pics later as they are on my camera at home.

The problem I am having is, despite having an anti-siphon break (ASB) drilled in my return, water continues to be reverse-siphoned into the sump, passed the ASB. I am assuming it is retaining enough pressure to keep siphoning water in the return jets. The problem is, any bigger of an ASB and I will have too much flow coming from it, so I may have to rebuild my return.


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## RRasco (Aug 31, 2006)

duplicate post, disregard


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## CichlidRI (Sep 7, 2002)

Honestly, I would put a true union check valve on the return pump so it couldn't start a syphon on power failure. But i've done your method before. You will probably have to drill another hole or make the one you put in it larger.


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## RRasco (Aug 31, 2006)

I'll probably try increasing the size of the ASB on this return. I will more than likely be revamping all of this as I get more experience in how they work. My first sump, all DIY.


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## CichlidRI (Sep 7, 2002)

This is what you would need. It won't reduce the flow to your spray bar as will be the outcome by drilling hole bigger for the anti syphon.

The water will only flow one direction. If it goes the wrong way, the ball blocks the flow.










Only thing I've noticed with these is if you put them too close to your return, they will rattle. Can be fixed by replacing the plastic ball with a rubber one of the same size.

PS: You could also look up true union ball, true union swing, true union check valve.


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## mightyevil (Oct 23, 2008)

Hmmm... Are you sure the water that is being returned to your sump is coming from the output? I would not blame it unless you have seen it physically.

Siphon overflow boxes are tricky, especially when they are DIY. Since the siphon is slow it may be drawing water from the overflow box in the tank slowly enough for you to not notice it but the level in the sump is getting higher.

If you can provide a quick video, it would probably help a lot since we are trying to figure this out practically blind folded. opcorn:

Oh and the reason why the durso may not be working is because it is too high and the water level in the box where the durso is gets higher with the durso on, this creates water pressure which slows down the siphon.


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## mightyevil (Oct 23, 2008)

RRasco said:


> I'll probably try increasing the size of the ASB on this return. I will more than likely be revamping all of this as I get more experience in how they work. My first sump, all DIY.


I dont think it is the hole size at this point, I would wait if I were you.


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## RRasco (Aug 31, 2006)

I am pretty sure it is coming from the return, it happened while I had my ball valve closed on the intake. It was WAY faster filling up my sump before I drilled the ASB. It now happens extremely slowly.

Sure, I will take a video of it when I get home. I'll also post some pictures of my HOB overflow and durso to see if you have any recommendations regarding that.


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## RRasco (Aug 31, 2006)

I took a video last night, but in the process I was evaluating the setup a little more. I think you may be right, it might be draining down the intake. I think the inside box I have is not water tight and the minor siphon is allowing the water to seep through the loose seal and continue to siphon into the outside box and eventually drain into the sump. I am going to play around with it a little more today. I intend to build a new HOB overflow since my wier didn't work so good to begin with. I'm sticking with the U-tubes.


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## mightyevil (Oct 23, 2008)

Well, there you go :thumb:

Again, try and have your durso pipe as short as possible, this will allow the siphon to work faster.


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## RRasco (Aug 31, 2006)

Is that because the water pressure is greater?

Here is the video, so you can maybe suggest any other erroneous methods I employed; durso pipe not installed ATM.






How low should a durso stand pipe be positioned below the water surface? Mine was only an inch or two because I am using a HOB overflow. Most uses of durso pipes I have seen were in drilled tanks.


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## mightyevil (Oct 23, 2008)

Thanks for the video, I do have some questions and suggestions.

Does your siphon break if you let all the water go to the sump after the power outage simulation? You need to check on that. My suspicion is that it will fail and can overflow your display tank once the power is turned back on because there is no more siphon.

The reason why I think it would fail is because the water in the interior and exterior overflow boxes must reach the same water level in order to stop siphoning but at the same time there cannot be any pressure from the water in the display tank pushing down on the water in the small interior overflow box because that pressure will cause a siphon, in fact this is how this type siphon is designed to work, by pressure.

*Option 1*
I did not think that your interior overflow box was going to be so tiny. In your case, your Durso pipe will have to be taller, not shorter (I was giving advise blind before, sorry for that). The Durso will have to come up but just below the waterline in your interior overflow box. Your siphon will be a lot slower than what you have now but it will be safe and you will have to reduce the output on your pump to prevent overflowing your tank due to the fact that the siphon will not be able to handle that much water going through it.

*Option 2*
Rebuild your overflow and have it come lower on the interior side, this way you can let your pump push its maximum amount of water which will make the water level in the tank rise and create the pressure it needs for the siphon to handle the load of water.

*Option 3*
Keep researching and make it work, maybe some valves that will keep the water from reverse siphoning...


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## mightyevil (Oct 23, 2008)

Here is my system...









My Durso is too high but that was as low as I could go with the exterior overflow box I made. My return is slow, a heck of a lot slower than I wanted but I am too lazy to fix at this time. My solution would be to either get rid of the Durso and add a piece of acrylic to the middle of the box which would only be 2" high and it would improve my flow but the noise would be annoying. Another fix for me would be to make my exterior overflow box deeper so the Durso is not too high and allow less water pressure in that box which will increase the flow of water through the system.

I thought you had a similar problem but your problem is based more on the interior overflow box.


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## fox (Jun 11, 2009)

The siphon broke. From the vid the water level stalls at the ASB. It also appears the HOB stops draining at the level of the standpipe.

If you leave the power off longer does the water level drop any lower than the ASB.

My sump continues to rise for a moment after the siphon breaks but the tank does not drain lower, the water trapped in the horizontal sections of my drains take a bit to completely settle. I did not put them on enough of an angle , mebbe you are experiencing this also?

I keep my durso's as high as I can since I hate the noise of the waterfall over the weir.


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## mightyevil (Oct 23, 2008)

What I mean by siphon break is, does the water in the U-tube also drain out? Do you have to suck (or whatever method you use) on the flexible tubing to get water back into the U-tube? That is my concern because if that does happen then your display tank will overflow once the power is restored if you are not there to help otherwise. The U-tube should remain filled with water during a power outage so when the power turns back on, the water level in the display tank will rise, cause pressure and start siphoning water once again automatically without your assistance.


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## RRasco (Aug 31, 2006)

My siphon does not always break, but it has. I think part of my problem here is that for the siphon to stop (for the overflow) the water level would have to rise above the standpipe since that is how low the inside box of the overflow is. So this causes the overflow boxes to never be able to have the same water level. I tried a higher standpipe, but it was too close to the top of the outside box for comfort. I am planning to rebuild my overflow now that I have a little more operating experience. For now, I purchased a HOB overflow so I can:

1) have a system that will not overflow should I experience a power outage
2) so I can see how a HOB is supposed to work.

I plan to build a dual U-tube and drain system to ensure my drain is faster than my return pump, which currently, if allowed to run on an open PVC (non-spray bar) would be faster than my drain is currently. My spray bar fell off once and my tank was filling up very quick! I need to cement my spray bar to the return pipe. In the meantime, I will use my store bought overflow and probably move it to my 29g once I begin working on that setup again and rebuild one for the 110g.

Thanks for all your help guys!


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## mightyevil (Oct 23, 2008)

:thumb:

No problem!


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