How is a drilled overflow more reliable than siphon?

[NancyFish]

It seems most people would take a drilled tank (I’m still on the fence about attempting).

My thought is, they’re both overflows, I know the siphon can get air in it - but I feel like I’m missing something. What makes the one that much better longevity wise?

Does a HOB overflow still have the chance of flood if the return pump has a float switch?

 

[Serpentman2024]

A drilled drain is below the water line so unless its blocked or the return pump flow rate exceeds its capacity, it will reliably drain 100% of the time. A siphon based HOB overflow runs the risk of air bubbles, etc. braking the siphon. Although a float switch helps mitigate this risk, it is another potential point of failure as switches can get stuck.

 

[SpyC]

It seems most people would take a drilled tank (I’m still on the fence about attempting).

My thought is, they’re both overflows, I know the siphon can get air in it - but I feel like I’m missing something. What makes the one that much better longevity wise?

Does a HOB overflow still have the chance of flood if the return pump has a float switch?

How would the float switch on the return prevent an overflow?

I ran a hob overflow for a few years withiut any issues and multiple power outages. The catch with hob overflows is you need to properly start the siphon and not allow air to get in over time or else it will break and overflow the tank. Even too slow of a flow through the overflow can cause air to become trapped in it. Algae growing in the tube is also a concern. You want a clear tube so you can inspect and ensure proper siphon. A black tube will not allow this, but woul prevent the algae growth. Some folks messed with adding an aqualifter to maintain a siphon, but that introduced other potential failures.

A drilled tank eliminates these concerns and adds a decent piece of mine.

 

[Joe31415]

A) Float switches have a bad habit of getting stuck down. Don't use them in a place where failure is going to cause a problem. Optical switches can get dirty as well, but in general, I think most people have better luck with them. If I were doing this, I'd probably use two with one set higher than the other and set up such that either of them detecting water will shut off the pump.

B)A drilled tank has a giant hole near the top. Of course, once we're past the drilled hole OR the siphon, you can run into the same problems (clogged overflow drain etc), the chances of the drilled hole getting clogged up enough that the tank overflows is considerably lower than losing the siphon, at that would be my assumption, though I've never looked into it.

 

[Tonycass12]

It seems most people would take a drilled tank (I’m still on the fence about attempting).

My thought is, they’re both overflows, I know the siphon can get air in it - but I feel like I’m missing something. What makes the one that much better longevity wise?

Does a HOB overflow still have the chance of flood if the return pump has a float switch?

Drilling tanks is super easy. Just take your time and don't use much pressure. Plenty of how to videos to watch. I would never trust a siphon in a power outage situation. We had storms blow through last night and the power went on and off a few times. My tank with standard overflows has no problem starting right back up when the power comes back on.

 

[Doctorgori]

the risk of air in the system vs gravity failing
the former is a possibility, the latter is a impossibility

 

[Joe31415]

Also, I would assume one of the big problems with using a siphon is a power outage. If you're not around to restart the siphon when the power comes back on, that could be a problem.

Now, I've never used a siphon system before so maybe there's a standard way of dealing with this, but if it were me, I think I'd want to set something up so if the pump loses power, it needs to be restarted manually.

 

[Joe31415]

How would the float switch on the return prevent an overflow?

The float switch goes in the [display] tank. If the water level rises and trips the sensor, it cuts power to return pump.

OP, keep in mind that if you do something like this, in addition to anything you need to do to restart the siphon, you'll also have to hold the float down or the pump won't have power. Come to think of it, that would be one of the few reasons to use a float switch (because how do you keep water away from the optical one). An override switch would also work.

 

[SpyC]

The float switch goes in the [display] tank. If the water level rises and trips the sensor, it cuts power to return pump.

OP, keep in mind that if you do something like this, in addition to anything you need to do to restart the siphon, you'll also have to hold the float down or the pump won't have power. Come to think of it, that would be one of the few reasons to use a float switch (because how do you keep water away from the optical one). An override switch would also work.

My brain went to the float in the return section and if it trigged from the return section emptying of water it would shutoff the pump, but at the point the display could be overflowing.

You don't need to restart the siphon in the even of a power outage, but there is always a risk that it could fill with air from being improperly setup. Example: the shorter end is in the overflow box and not the surface skimmer box. I know this was a common occurrence at the shop I used to work at a decade ago. Another is an improperly sized return for the overflow. Too little flow is just as bad as too much.

 

[NancyFish]

My brain went to the float in the return section and if it trigged from the return section emptying of water it would shutoff the pump, but at the point the display could be overflowing.

You don't need to restart the siphon in the even of a power outage, but there is always a risk that it could fill with air from being improperly setup. Example: the shorter end is in the overflow box and not the surface skimmer box. I know this was a common occurrence at the shop I used to work at a decade ago. Another is an improperly sized return for the overflow. Too little flow is just as bad as too much.

A) Float switches have a bad habit of getting stuck down. Don't use them in a place where failure is going to cause a problem. Optical switches can get dirty as well, but in general, I think most people have better luck with them. If I were doing this, I'd probably use two with one set higher than the other and set up such that either of them detecting water will shut off the pump.

B)A drilled tank has a giant hole near the top. Of course, once we're past the drilled hole OR the siphon, you can run into the same problems (clogged overflow drain etc), the chances of the drilled hole getting clogged up enough that the tank overflows is considerably lower than losing the siphon, at that would be my assumption, though I've never looked into it.

Say I drilled the overflow part, how encouraged is drilling the return hole vs an overhang return and not taking the chance twice drilling?

 

[michigan-reef]

My first tank had a hang on the back siphon overflow. That tank was running for about 15 months with no major problems, however I had to regularly restart the siphon to eliminate the air that accumulates in the top of the u tube. All the tanks I have owned since then have been drilled. Most of them I have drilled myself. A siphon overflow is a point of failure that is easily eliminated with a drilled overflow. As others have said drilling the hole in the glass is quite easy, just take your time. I practiced drilling a 10 gallon tank a few times to build up confidence. Also look up videos on how to tell if the glass is tempered. All you need is your phone (white image) and polarized sunglasses.

 

[NancyFish]

My first tank had a hang on the back siphon overflow. That tank was running for about 15 months with no major problems, however I had to regularly restart the siphon to eliminate the air that accumulates in the top of the u tube. All the tanks I have owned since then have been drilled. Most of them I have drilled myself. A siphon overflow is a point of failure that is easily eliminated with a drilled overflow. As others have said drilling the hole in the glass is quite easy, just take your time. I practiced drilling a 10 gallon tank a few times to build up confidence. Also look up videos on how to tell if the glass is tempered. All you need is your phone (white image) and polarized sunglasses.

Have you ever broke one? Everyone keeps saying it’s easy, and we have a drill but I keep feeling like it would be a setback (but I guess no different than 1-2 $$$ fish dying in the long term

 

[exnisstech]

The tank in my show case has been running on two hob overflows from the start. I've never lost a syphon and the only way I can create a loss of syphon is by lifting the tubes out of the water so they suck air. That said I would not use hob overflows again unless I had to. They're just too loud. At least my eshops are. I've tried all the different tricks to quite mine down but they are still very loud. I've gotten used to the noise would drill or buy drilled in the future. I've drilled to add an external return pump on a basement sump and it's actually pretty easy.

 

[ca1ore]

I haven’t used a siphon-based overflow in decades. Presumably they are more reliable now than they used to be (though imagine they are still ugly). Are you planning to use a controller? Even with an integrated overflow system, I still run multiple, redundant float switches. An optical switch in the display to monitor tank level and two standard floats in the sump to monitor level.

 

[ScottJ]

I've used a Lifereef overflow on a tank for over a year without a problem. The siphon has never broken, nor has any air collected in the tube. To prevent an overflow situation should it ever break, I only have as much water in my return chamber as the tank will hold. In other words, the return would run dry before it would pump enough water into the display. Also, my ATO cuts off after a certain run time (I think most of them do, but Tunze does)

As far as restarting, never had an issue. I turn off the return often, feeding corals, water changes, sock changes, and always restarts without a problem. The only time I have had to manually start it is when I've removed the tube to clean it (like twice a year)

Now, there are things that some people wouldn't like. It's not silent and you can see it above the top rim of the tank. But I'm fine with those. The tank is in the living room and we usually have music on. Also, I have it set up with the box at the end, it's a 55 gallon, and my sump is next to the tank, not under (long story). The whole thing is pretty unobtrusive the way we have it set up, so it's no big deal.

Can't say enough good about Lifereef stuff. Check him out.

 

[SpyC]

Say I drilled the overflow part, how encouraged is drilling the return hole vs an overhang return and not taking the chance twice drilling?

Drilling is very easy as long as you go slow (let the weight of the drill do the work), keep the bit wet, using a diamond bit, keep the drill at a lower catch setting so it doesn't try tearing/ripping when you hit a small snag or push, and the tank is NOT tempered. I think most overflows you need to drill for come with a template which makes it even easier. oh, and put cardboard or a towel in the tank to catch the bit of glass that you cut out so it doesn't hit the other pane.

You can always practice on a small cheap tank.

 

[PotatoPig]

My thought is, they’re both overflows, I know the siphon can get air in it - but I feel like I’m missing something. What makes the one that much better longevity wise?

Does a HOB overflow still have the chance of flood if the return pump has a float switch?

The air getting in is the issue. If I run the return pump too low I tend to see air acclimating over time - so have to run a minimum speed to guard again that. A drilled overflow doesn’t experience the same issue.

In terms of flood prevention… my preferred method is to set the sump baffles and water level so that a total failure anywhere in the system will overflow neither the sump nor the DT.

Also, I would assume one of the big problems with using a siphon is a power outage. If you're not around to restart the siphon when the power comes back on, that could be a problem.

Unless this is a multiple day outage this shouldn’t be an issue. If there’s no flow the siphon will (well, should unless there’s a serious issue with it) sit there primed and ready to go.

A bigger risk is low flow, where tiny bubbles from the water flow into the inside box can accumulate of the flow is very low as they don’t get swept out, IME this is a risk below about 1/3 to 1/4 the max flow rate for the siphon.

 

[Doctorgori]

I cut my teeth on Supreme Superkings; a 4 siphon HOB monster with a dangerous exposed metal motor…it could go months w/o breaking siphon, but eventually it would.
can’t tell you how often I used that wooden siphon starting thingy with the plastic hole cover to start up a u tube

I’ve also had several incarnations of overflow setups,
…give the effort time and investment in a reef tank, I wouldn’t depend on a manual u tube type siphon…just my opinion