Is a siphon returning water to the sump inherently bad?

[minitank]

I see posts all over the place saying that a siphon is very dangerous. My situation is that with a Durso pipe so much air is being sent into the sump I have uncontrollable micro-bubbles. After much tinkering I replaced the cap on Durso with one with no hole and it now siphons on purpose. The water drains very quickly and quietly and with zero air entering the sump. When I turn off the pump the water level drains and as long as it doesn't overflow the sump (not even close) before the siphon breaks. Upon turning the pump back on, the tank level rises and the siphon is automatically reestablished.

Is there anything in apparently dangerous about this set up?

 

[ca1ore]

A siphon is 'dangerous' only if it is the only drain - in other words, with no backup. The reason for this is really self evident. A siphon drain only works if said drain is perfectly matched to the pump return; so any further occlusion of the siphon means it will not be able to keep up with the return .... and there is no place for the extra water to go. Now, to some degree a siphon is self regulating - as the water head builds above the opening the capacity increases, but this is quite limited and quickly overwhelmed with even a partial blockage. While an open channel, durso style drain is less than ideal as the sole drain, it does have much greater capacity to handle partial blockages.

 

[Clowning_Around]

The biggest concerms im aware of are flooding either the suml and/or the DT depending on circumstances. It sounds like you have the sump sized correctlu so that it womt flood in power outage. That leaves the oposite pump runs with siphon broke and pump floods DT and potentially runs pump dry damaging it too. The second item is however not neceassirly directly related to siphon systems so much as to the how its being managed, there are a lot of siphon mwthods, some good some bad. It sounds like your on the right track

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[journeyman]

A siphon is bad if your pump ever fails and the water from your tank siphons back into your dump and overflows the sump. This can result on water damage and/or electrical fires, and other bad things... You can prevent this by creating a siphon break.

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[minitank]

A siphon is 'dangerous' only if it is the only drain - in other words, with no backup. The reason for this is really self evident. A siphon drain only works if said drain is perfectly matched to the pump return; so any further occlusion of the siphon means it will not be able to keep up with the return .... and there is no place for the extra water to go. Now, to some degree a siphon is self regulating - as the water head builds above the opening the capacity increases, but this is quite limited and quickly overwhelmed with even a partial blockage. While an open channel, durso style drain is less than ideal as the sole drain, it does have much greater capacity to handle partial blockages.

Thanks for your comments, I think its more correct to say that rather than being "perfectly balanced" that its important to have excess capacity in the drain beyond what the pump can produce.

Curious, how would a vented durso be less susceptible to blockages than the siphon? fyi, i simply took a durso design and changed the vented cap to a non-vented cap resulting in a siphon.

 

[minitank]

A siphon is bad if your pump ever fails and the water from your tank siphons back into your dump and overflows the sump. This can result on water damage and/or electrical fires, and other bad things... You can prevent this by creating a siphon break.

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I find it impossible for that to happen in my setup. While the pump is on, the water enters the siphon a few inches from the top of the display tank. When the pump is turned off, the siphon continues until the water drops and the siphon naturally breaks. In this respect, it works identically to a vented durso.

 

[ca1ore]

Thanks for your comments, I think its more correct to say that rather than being "perfectly balanced" that its important to have excess capacity in the drain beyond what the pump can produce.

That's not how a siphon works, though. Perhaps you are using the term incorrectly. A siphon, by definition is a pipe that is full of water, with no air representing the maximum that can flow based on the physical constraints; so there is no material excess capacity. The only way to increase flow is to change those physical constraints, by extending the drop, increasing the amount of head pressure over the pipe or increasing the diameter of the pipe. Of those three things, the only one that happens 'automatically' is the head pressure - and the excess capacity supplied is quite small.

 

[journeyman]

I find it impossible for that to happen in my setup. While the pump is on, the water enters the siphon a few inches from the top of the display tank. When the pump is turned off, the siphon continues until the water drops and the siphon naturally breaks. In this respect, it works identically to a vented durso.

Hence the last sentence in my comment...[emoji6]

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[Clowning_Around]

A siphon is bad if your pump ever fails and the water from your tank siphons back into your dump and overflows the sump. This can result on water damage and/or electrical fires, and other bad things... You can prevent this by creating a siphon break.

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Backflow preventer.

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[der_wille_zur_macht]

Curious, how would a vented durso be less susceptible to blockages than the siphon? fyi, i simply took a durso design and changed the vented cap to a non-vented cap resulting in a siphon.

The durso is "less susceptible" in the sense that it has excess capacity. Let's say it's running at 50% full of water and 50% full of air. Well, you can cause up to a 50% blockage and it'll still manage to regulate and handle the extra water flow.

On the other hand, if you have a siphon, ANY percent blockage (even possibly just 1 or 2% from some microbibbles, or algae growing in the tube over time, etc) will essentially cause the system to become unbalanced, and you end up with water on the floor.

A Durso can self-regulate over a very, very wide range of flows. That's why they are popular in pre-manufactured drain systems, it's foolproof - you can slap any old pump in the sump, up to a known max flow rate, and it "just works" without any tuning or knowledge required. Drain systems that rely on full siphons, on the other hand, REQUIRE tuning to balance the siphon to the return pump - usually, this happens in the form of a gate valve on the siphon line. Once tuned, the system is only able to self regulate over a very, very narrow range of flow rates - the window is literally a few percent, versus close to 100% for a Durso.

If you're telling us you have a system with a single full siphon line and no other drain, and the siphon is not tuned or adjusted in any way to match your return pump, and it's "just working" in the sense that the siphon is keeping up exactly with the return pump, one of two things is possible here. One, you're both very lucky and on the verge of a major catastrophe, or two- there is still somehow air making it's way into the drain (allowing it to still function like a self-regulating Durso) and you're just not aware of the path.

 

[ca1ore]

Backflow preventer.

If by 'backflow preventer' you mean some kind of mechanical check valve, I would strongly discourage the practice. Inevitably check valves foul and fail to prevent the very thing you bought them to prevent. An anti siphon hole is better, and the mouth of the return just below the surface of the water even better still.

 

[Clowning_Around]

If by 'backflow preventer' you mean some kind of mechanical check valve, I would strongly discourage the practice. Inevitably check valves foul and fail to prevent the very thing you bought them to prevent. An anti siphon hole is better, and the mouth of the return just below the surface of the water even better still.

I see your point but I have a questions about this suggestion still yet. So take my application, I'm using locline after an over the trim return. In this configuration i would place a hole in my pipe under the water just before the first locline fitting if i understand you correctly. So then in normal operation mode my pump is pushing the water through the pipe and ultimately out the end of my locline nozzles, meanwhile i have a small amount of water spewing through a smaller openig further back in the return line under the waters surface, presumably pointing down in the tank? So now if that understanding is correct, then in power loss a reverse drainage begins from the DT via siphon back to the sump until the water in the DT drains low enough such that it exposes this whole to air but would the same thing occur from the opening at the end of the return outlet, in my case the locline nozzles? Otherwise you have a hole higher and water spraying issue? What am i missing here? The check valve hopefully albiet not foolproof add you've pointed out hopefully stops that extra top lathe from the DT before the return supplies opening is exposed to air.

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[karimwassef]

You always need three pipes - a siphon, a slow flow, and an emergency.

This always works unless your pipes are too small to handle the return pumps/surge/other.

 

[minitank]

Addicted to siphon?

Addicted to siphon?

Perhaps I have a perfect setup on the verge of disaster but I have become addicted to the absolutely pristine lack of bubbles in my sump and display.

The risks outlined above seem to be centered around the possibility of display overflow. What do you think of attaching a diy float valve to the pump? This would cut off in the case of high water in the display because of inbalance, blockage or any other reason.

 

[ca1ore]

I see your point but I have a questions about this suggestion still yet. So take my application, I'm using locline after an over the trim return. In this configuration i would place a hole in my pipe under the water just before the first locline fitting if i understand you correctly. So then in normal operation mode my pump is pushing the water through the pipe and ultimately out the end of my locline nozzles, meanwhile i have a small amount of water spewing through a smaller openig further back in the return line under the waters surface, presumably pointing down in the tank? So now if that understanding is correct, then in power loss a reverse drainage begins from the DT via siphon back to the sump until the water in the DT drains low enough such that it exposes this whole to air but would the same thing occur from the opening at the end of the return outlet, in my case the locline nozzles? Otherwise you have a hole higher and water spraying issue? What am i missing here? The check valve hopefully albiet not foolproof add you've pointed out hopefully stops that extra top lathe from the DT before the return supplies opening is exposed to air.

The problem with the check valve is that over time shmutz builds up/grows on the seating surfaces, thus preventing a perfect seal. In the event of a protracted outage, significant tank volume can siphon slowly back down to the sump. This can be mitigated somewhat by regular cleaning of the valve, but using an anti siphon hole or a return outlet mounted closer to the surface is much better. Plus, dispensing with the check valve removes some back pressure on the pump - particularly since you are using locline which is really good at robbing you of flow.

The best, and mostly fooproof, approach IS to have the mouth of the return close to the surface of the tank so that it acts as the siphon break (my locline-less return pipe is only 1/2" below the water surface). Even a dedicated siphon hole can get clogged. If you go with a siphon hole, drill it underneath the return pipe so that the spray is directed downwards.

 

[ca1ore]

Perhaps I have a perfect setup on the verge of disaster but I have become addicted to the absolutely pristine lack of bubbles in my sump and display.

The risks outlined above seem to be centered around the possibility of display overflow. What do you think of attaching a diy float valve to the pump? This would cut off in the case of high water in the display because of inbalance, blockage or any other reason.

A float valve certainly could help to prevent a potential display overflow. The other option is the reconfigure your drains. You could, for example, repurpose the return (assuming it is coming up through a hole in the overflow) as a backup drain and go over the rim for a new return.

 

[Clowning_Around]

Thanks, you confirmed a few things for me.

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[SGT_York]

Some confusion in this post. The OP is talking about an intermittent siphon on the drain pipes, not a siphon in the return line, a check valve is irrelevant to this conversation, that advice is only good on the return line (albeit still a bad idea waiting to fail)

The other confusion is the misapplication of a Herbie or Bean Animal Setup. MiniTank I highly encourage you to look at those two types of specific drain systems, both will eliminate all bubbles into your sump far more than either a durso or your intermittent siphon ever will be able to do. Your current setup won't eliminate the inherent bubbles during start up or breaking the siphon it also has the downside of fluxuating the water level in your sump, that will give you issues with top off levels and general stabilization assuming your protein skimmer is outside the final sump section.

The herbie and Bean Animal setups use a valve to restrict the siphon flow so it matches exactly the return rate of your main pump, the problem with it is snails tend to enter the pipe and get stuck at the valve, which is why you need a secondary drain, Bean Animal's setup uses three drains but is difficult to implement into an established tank.

I'd recommend the Herbie setup as it only requires two drain pipes, you won't be disappointed, another benefit is that both these systems are absolutely silent, you won't hear a thing from the pipes.

Best of luck and most important, enjoy!

 

[mcgyvr]

I run be an animal drains and I can not lie..
You other drain systems can't deny
When a snail climbs in with its shell on its back
And a clump of bubble algae following that
You are done....
Time to clean the floor

 

[ca1ore]

Some confusion in this post.

Just the 'living' nature of these threads sometimes.