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LF HOB overflows and opinions

richiev

Supporting Member
Anyone have experience with hob overflows? I'm considering adding one to my 24x24x12 frag tank (I don't want to drill, especially because it's in use). I'm leery it's asking for a flood. I have an extra sump I can use though, so it's an attractive idea.

Anyone have experience with any they'd recommend? Anyone have any they're looking to get rid of?
 

Arvin R

Treasurer
BOD
I use a HOB overflow on my 25gal lagoon tank. Eshopps pf-800. I have only had one instance of the siphon breaking and that was due to my skimmer overflowing sending a tin of microbubbles into the tank. Luckily the ATO beeping woke me up and I was able to notice it and shut the pump off. I now run it with a Varios pump and have the float valve set to shut off the
pump if return pump chamber gets low to prevent an overflow. With this setup I feel pretty safe from the issues a HOB. I do eventually want to actually hard plumb it with a gate valve as it's pretty loud and in my bedroom. I was going to only run it temporarily and eventually drill the tank but I go by the saying "don't fix what ain't broke" (I'm also a lazy bastard sometimes lol)

I did have to prop mine up with a jenga block to get my water level to a more acceptable height compared to the top of the glass. As the slotted adjustment wasn't able to let me raise it up where I wanted.

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RandyC

Supporting Member
HOB overflows scare me more than drilling…. :)

If you do drill, go marine modular (if you can handle the wait time). I am not a fan of eshopp (drilled) overflows at all.
 

Reefinglens

Supporting Member
I agree to just drill it. Also if you do go eshopps drilled, just place the template higher than recommended so the water level isn’t so low.
Since your tank is currently in use though, an alternative is a HOB AIO like this one from Aquamaxx.


I personally wouldn’t trust a hob overflow I spilled a gallon of water before and that was a pain to soak and clean up let alone several gallons on the floor, no thanks!

edit: I’ve been running one of these Aquamaxx HOB AIOs on a 40 breeder for over a year now and it’s been great. I’ll actually be taking that tank down soon though
 
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RandyC

Supporting Member
I agree to just drill it. Also if you do go eshopps drilled, just place the template higher than recommended so the water level isn’t so low.
Since your tank is currently in use though, an alternative is a HOB AIO like this one from Aquamaxx.


I personally wouldn’t trust a hob overflow I spilled a gallon of water before and that was a pain to soak and clean up let alone several gallons on the floor, no thanks!

edit: I’ve been running one on a 40 breeder for over a year now and it’s been great. I’ll actually be taking that tank down soon though

It’s not the water level of the eshopps. Their design makes it difficult to silence the drain. You’ll have to add a taller standpipe on the e-drain to silence it which will lead to salt creep coming out the top.
 

Reefinglens

Supporting Member
It’s not the water level of the eshopps. Their design makes it difficult to silence the drain. You’ll have to add a taller standpipe on the e-drain to silence it which will lead to salt creep coming out the top.
I agree when it comes to the large given there are 3 drains, which I used on a previous tank. I just added PVC to the main drain to leave the pipe ans open and possible, used the e-drain that it came with as the secondary drain and made a taller e-drain. But a small or medium are easily silenced right out the box with a gate valve installed.

For larger tanks I prefer the Synergy Shadow
 

RandyC

Supporting Member
I agree when it comes to the large given there are 3 drains, which I used on a previous tank. I just added PVC to the main drain to leave the pipe ans open and possible, used the e-drain that it came with as the secondary drain and made a taller e-drain. But a small or medium are easily silenced right out the box with a gate valve installed.

For larger tanks I prefer the Synergy Shadow

Even with a gate valve, without adding a larger standpipe, it was not possible to silence the waterfall from the bulkhead to the external overflow box. A larger standpipe will work, but puts the water level of the external overflow box close enough to the top that salt creep a mess over time. This was a few years ago in the eclipse models, but it doesn't seem like they changed the design and from first glance of the prodigy line of overflow boxes, it suffers from the same problem.
 

richiev

Supporting Member
I have drilled tanks before, and have the bits. Though much of that was on small tanks with really thin glass that crack instantly. However, that's a ton of hassle at the moment. I'd need to drain everything so I could be safe in case something cracks, as well as to get it into position where I could securely hold the drill. Given the size of the tank that wouldn't be the end of the world, but if a a HOB option would work it'd mean I could get the sump in action, add a bunch of water volume, a giant refugium, and decide if I want to drill another day.

This is making me think it'd be really nice to have a coast to coast ghost overflow on there some day. If I had a HOB overflow I'd probably try and replace the inside the tank section with a wider one which I could 3d print. I like the wide overflow aesthetic.

If the consensus is they all suck, that's fine too though.
 

richiev

Supporting Member
This is maybe a dumb idea, but having now looked at HOB overflows you can buy, and diy ones made out of pipe, and a couple 3d printed options, I think I'm going to try building my own. Unless someone tells me they really love theirs or a great trick to drill in place.

It seems like this would be pretty easy to 3d design and a fun project. I'd base it off of https://www.reef2reef.com/threads/this-guy-want-a-beaslbob-trap.36891/

I can have a wide overflow weir. I'd do one or two wide 3d printed pipes leading from the in tank section over to the back reservoir. I'd then do a Herbie setup in the overflow box to drain into the sump.

Because it'd be 3d printed, I should be able to keep it pretty low profile in the tank.

This is definitely going to end up with my floor flooded, but luckily it's in a tile office that's basically a garage!
 

Arvin R

Treasurer
BOD
You'll want the overflow tubes to be clear so you can verify you get all the air out of them when you prime the siphon tubes and I don't know the ideal measurements but you'll obviously want the siphon tube exit some bit lower than the front that will go into the internal weir box.

Check up Life Reef overflows and see if they talk about design choices at all. From my research I've done his HOB overflows have no reported siphon breaks/failures. Size of tube will probably be biggest determination and you'll want the diameter to be as small as possible while still being able to flow the gph you want your system turnover to be. Also close off the top of the internal overflow weir box so that a snail or something else can't crawl in and clog your siphon tubes (another reason to have them clear is so you can always visually see they are not building up gunk that could lead to a clog)

Other factors that I took into account is using a sump with adjustable baffles to set chamber water levels and I run my return chamber very low as my display tank water level is very high. Basically you'll want to make sure that your display can take all the water from the return chamber and not overflow. And of course the key IMO is the Varios pump and their float switch to kill the pump once the return chamber water drops.

As we all know float switches can fail so I'm always checking mine for proper operation by pulling it out of the water and making sure it shuts the pump off and can freely move up and down whenever I'm doing maintenance. The controller also has a light to show when it's in the "pump off" position and another light to show that you indeed have the safety switch feature activated.

If you're gonna run a skimmer on this system I also advise using a reef octopus and use the float switch to kill the skimmer pump when the collection cup is full.

Other potential safeties is an Apex or other controller with leak detector to shut pump off incase of overflow.

With that all being said, drilling a tank is not hard and still the preferred method for overflow and eliminates all the failure modes of a HOB overflow with the exception of the drain tubes getting clogged. You should easily be able to drain enough water to do the job without emptying the tank. And I prefer drilling in the vertical position with a drip line setup to keep it wet as the chips clear out and provide a cleaner cut imo. (@Da_Neefer will agree to this to as he did drill a tank with everything still in).
 

richiev

Supporting Member
This is 100% opening me up for well-deserved "I told you so" statements, but I picked up an eshopps single drain HOB overflow off CL ($20) and have been a bit frustrated with it. It actually runs 100% completely silent, and having tested it it seems very loss-of-siphon protected, however the problem I'm having is inconsistency in my return section's water height. This may be because of the pump not being consistent, but for now I'm blaming my HOB overflow.

The main reason I'm noticing it is I have my reef-pi acting as my ATO, and it alerts if the dc pump I'm using for ATO (a cheap peristaltic) runs too long. Initially I had it set to alert after 30 sec, because pre-sump install it would usually run for ~5sec at a time. Slowly I've upped it more and more until now I have it set to run for upwards of 5 minutes before alerting. Now in 5 minutes it's not actually putting that much water out (the peristaltic pump is intentionally not strong), but it's just annoying me to no end.

So kinda dumb question, but is there any real reason why a HOB overflow would be more inconsistent in draining to sump speed than a drilled overflow? I know the water level in the HOB overflow itself is varying, but I'm not sure if that's a symptom of all this or a cause.

The only thing I can think is that a drilled overflow would have less possible ways for the water level to vary. Eg right now the places that could vary are:

  1. highest level -- the main display (but not much, since the in-tank weir overflow controls that level)
  2. second highest -- the in-tank weir overflow area
  3. third highest -- the HOB overflow reservoir -- theoretically from a siphon this should be almost the same height as #2
  4. lowest level -- the return section of my sump
A drilled tank would always have 2&3 be the exact same height, removing one possible variation.

And yes, I did order a drill bit, but before doing it I want to play with this a bit more, and still need to acquire an external overflow.
 

Arvin R

Treasurer
BOD
An inconsistent return pump would cause this. I don't have that issue with mine. Single drain eshopps pf-800. I run it at full siphon so it's silent. Using a Varios-2 return pump.

The only other thing I could think that might cause this is if your return plumbing is too oversized for your flow rate and you have to choke down the gate too far so it's almost shut.
 

richiev

Supporting Member
An inconsistent return pump would cause this. I don't have that issue with mine. Single drain eshopps pf-800. I run it at full siphon so it's silent. Using a Varios-2 return pump.
I wish I had a way to validate this, and I think it's probable, but on the other hand I had this pump running on my reefer 170 for awhile and didn't knowingly have this issue there. On the other hand, maybe it was happening all the time and I just didn't know, because that was using a gravity ATO and not one I was monitoring.

The only other thing I could think that might cause this is if your return plumbing is too oversized for your flow rate and you have to choke down the gate too far so it's almost shut.
That too is possible. It's plumbed with a 1in return. I was debating if this could be the cause, and did ramp up the return pump higher so that I could open the drain more.

Though I'm not sure if we're thinking the same thing. When you say "return" do you mean "primary drain line" or "line attached to the pump which is flowing into the tank"?
 

Vincerama2

Supporting Member
I used an HOB overflow on my 10g nano tank when I first started in the hobby. I think it flooded at least four times.
Things I learned;
1) You must absolutely find a failsafe. You need a way to shut off your return pump if you detect low water levels. With modern controllers that shouldn't be hard at all. I'm sure an Apex can easily shut off the pump and alert you. Otherwise ... flood city!

2) You have to use a fairly high flow rate and at a rate that is managable by the overflow pipe (the U shaped thing). This is because if you use a slow flow rate, bubbles will get trapped at the top of the overflow and accumulate until the siphon breaks and then ... flood city! With a smaller tube or faster pump, small bubbles get whooshed down the overflow without a chance to get stuck at the top of the overflow.
3) They can be loud, you'll need to make a "DURSO" standpipe to quite it down. An open standpipe in the overflow box will be loud

4) You should leave a gap between the exit of the over flow pipe in the sump and the surface of the water. This will be loud, but you can rig up another larger pipe around it or something. Why? Because you don't want back pressure from the water in the sump or any thing else to slow down the water flow or else .... flood city!

4) You cannot allow snails near the over flow or else .... flood city!



The only danger really is pumping your entire sump into your display tank. And as mentioned some sort of level controller would mitigate a lot of the danger. Having a water/flood alarm on the floor next to the tank is a must as well.

V
 

Arvin R

Treasurer
BOD
I wish I had a way to validate this, and I think it's probable, but on the other hand I had this pump running on my reefer 170 for awhile and didn't knowingly have this issue there. On the other hand, maybe it was happening all the time and I just didn't know, because that was using a gravity ATO and not one I was monitoring.


That too is possible. It's plumbed with a 1in return. I was debating if this could be the cause, and did ramp up the return pump higher so that I could open the drain more.

Though I'm not sure if we're thinking the same thing. When you say "return" do you mean "primary drain line" or "line attached to the pump which is flowing into the tank"?
Yes I meant primary drain line. Thank you for the correction and I'm glad you understood. Another thing I checked when adjusting flow on mine is to make sure the weir box water level was as high as I could get it while still being underneath the lowest portion of the weirs. This eliminated small air bubbles from going through the siphon tube which would end up getting sucked down the primary drain tube.
 

richiev

Supporting Member
I used an HOB overflow on my 10g nano tank when I first started in the hobby. I think it flooded at least four times.
Things I learned;
1) You must absolutely find a failsafe. You need a way to shut off your return pump if you detect low water levels. With modern controllers that shouldn't be hard at all. I'm sure an Apex can easily shut off the pump and alert you. Otherwise ... flood city!

2) You have to use a fairly high flow rate and at a rate that is managable by the overflow pipe (the U shaped thing). This is because if you use a slow flow rate, bubbles will get trapped at the top of the overflow and accumulate until the siphon breaks and then ... flood city! With a smaller tube or faster pump, small bubbles get whooshed down the overflow without a chance to get stuck at the top of the overflow.
3) They can be loud, you'll need to make a "DURSO" standpipe to quite it down. An open standpipe in the overflow box will be loud

4) You should leave a gap between the exit of the over flow pipe in the sump and the surface of the water. This will be loud, but you can rig up another larger pipe around it or something. Why? Because you don't want back pressure from the water in the sump or any thing else to slow down the water flow or else .... flood city!

4) You cannot allow snails near the over flow or else .... flood city!



The only danger really is pumping your entire sump into your display tank. And as mentioned some sort of level controller would mitigate a lot of the danger. Having a water/flood alarm on the floor next to the tank is a must as well.

V
I'm not actually concerned about flooding, but my setup might be different than yours. My tank can handle all my sump return area pumping into it, plus some, without overflowing. My sump can hold a ton of extra water, and the main limiter is actually how low I have my return line versus the overflow.

Are the flooding concerns people have with HOBs related to that, or something else? I could see somehow the HOB compartment itself overflowing, but I don't know how that could happen since it's a siphon. The tank would have to be overflowing for the HOB to still fill and drain.
 

Vincerama2

Supporting Member
I'm not actually concerned about flooding, but my setup might be different than yours. My tank can handle all my sump return area pumping into it, plus some, without overflowing. My sump can hold a ton of extra water, and the main limiter is actually how low I have my return line versus the overflow.

Are the flooding concerns people have with HOBs related to that, or something else? I could see somehow the HOB compartment itself overflowing, but I don't know how that could happen since it's a siphon. The tank would have to be overflowing for the HOB to still fill and drain.
If algae or a snail blocks part of the return line, then you can overpower the drain with the return pump. In your case, not a problem. Like I said I had mine on a 10g tank which has almost no margin for error!

V
 

Arvin R

Treasurer
BOD
I'm not actually concerned about flooding, but my setup might be different than yours. My tank can handle all my sump return area pumping into it, plus some, without overflowing. My sump can hold a ton of extra water, and the main limiter is actually how low I have my return line versus the overflow.

Are the flooding concerns people have with HOBs related to that, or something else? I could see somehow the HOB compartment itself overflowing, but I don't know how that could happen since it's a siphon. The tank would have to be overflowing for the HOB to still fill and drain.
The biggest concern is the siphon tube getting blocked by a snail or something else and then your siphon breaks. I have made my lid of my tank so that nothing from the DT can get into the weir box unless it can fit through the weirs.

But if your tank can hold the excess amount of water from your return chamber and you sump can hold all the water than siphons down from flow being off then I don't really see any issue.

Getting the return pump water level consistent is the only hurdle in your specific setup and once that is solved then you should have a smooth/safe running HOB overflow setup.

I am going to add one more safety to mine in addition to my low water level cutoff switch for the return chamber. I will add a high level safety switch to shut off the pump if the water level in my external overflow box gets too high. For my specific setup that should cover all possible flooding situations. My 1in gate valve has to be closed down pretty far (wish I went with a 3/4in drain line) so clogging/reduced flow can happen over time pretty easily I presume which would cause the water level in the external side of the HOB to rise.
 
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