HOB Dual Drain Overflow

[Fastpitch]

I have read most all the threads on HOB Overflows so I think I understand the risks. I am looking for advice on how to mitigate that risk since I will not be drilling my tank. I have a 150 gallon aqueon that is already established. I plan on moving out of state in about 5 years, so I will probably drill it then. In the meantime HOB will have to do.

My plan is to go with a dual drain Marine Depot OF-1200. I have a whole house permanent back up generator, so power loss is usually not an issue. The auto transfer switch on the generator usually trips in about half a second. My question is what steps make for the best HOB overflow set up? Is there customization I should make to the overflow? Should both drains be used fully at all times? Or should a Herbie drain be used? Is it possible to customize a bean animal third drain? Any suggestions on float switches, etc. (eventually I plan on an APEX)

Thanks in advance.

 

[malacoda]

Okay, a lot questions and different possibilities couched in there, so this is going to be a little lengthy, but here's what I learned from my HOB...

IMO, the only real risk with a HOB is having the overflow pipe(s) becoming blocked and causing the DT to spill over onto the floor.

This is easily avoided by ensuring the operating water volume of your return pump chamber is just a little but less than the vacant headspace in your DT...

That way, if the overflow U-tubes or drain pipes become blocked, your return pump will run out of water to send up to the DT before the DT overflows.

As a result, the worst case scenario would be the return pump running dry and burning out. Far cheaper and easier to replace a return pump than it is to replace a floor.

You can adjust the vacant headspace in your DT by raising or lowering the HOB. As you may have guessed, lowering it will lower the DT waterline thus giving you more vacant headspace. (The HOB would need to be adjustable.)

And you can reduce amount of water available to the return pump by simply removing some water from the sump ... as long as it doesn't cause your return pump to start drawing air.

That said, if your return chamber is really big (e.g. oversized for your tank), you may end up having too much volume in the return chamber to avoid overfilling the DT if the HOB pipe(s) become blocked.

If that's the case, the only other thing you can do is be sure to clean the U-tubes regularly to ensure no algae grows inside them. And check them regularly to make sure no air has slowly gotten trapped in them ... if there is you'll see an air bubble in the top of the clear U-tubes. The bigger the air bubble, the slower the siphon will be ... and the greater the chance the return pump will send water to the DT quicker than the HOB can drain it. THESE 2 MAINTENANCE steps should be done every month or two anyway.


As for whether or not to use both drains on the MD OF-1200, yes, BOTH DRAINS should be used at the same time. If you try closing off or blocking one of the drain pipes with a valve, the inverted U-tubes will pull water from the DT into the overflow box faster than the remaining drain pipe alone can drain it ... and the HOB box will overflow.

If you remove/shut-off both a U-tube and it's drain pipe ... leaving only one U-tube and one drain pipe in operation, then you will only be running the HOB at half-capacity and may not get enough turnover to adequately filter the water of a 150g.



As for adding a 'third' bean animal drain, that HOB doesn't have enough room to add an additional drain pipe. So, it wouldn't really be an option.


FWIW, I ran a Marine Depot Nano HOB on my 24g for four-and-a-half years without any issues whatsoever. They work great as long as you set 'em up right and clean them once in a while.

 

[Fastpitch]

Okay, a lot questions and different possibilities couched in there, so this is going to be a little lengthy, but here's what I learned from my HOB...

IMO, the only real risk with a HOB is having the overflow pipe(s) becoming blocked and causing the DT to spill over onto the floor.

This is easily avoided by ensuring the operating water volume of your return pump chamber is just a little but less than the vacant headspace in your DT...

That way, if the overflow U-tubes or drain pipes become blocked, your return pump will run out of water to send up to the DT before the DT overflows.

As a result, the worst case scenario would be the return pump running dry and burning out. Far cheaper and easier to replace a return pump than it is to replace a floor.

You can adjust the vacant headspace in your DT by raising or lowering the HOB. As you may have guessed, lowering it will lower the DT waterline thus giving you more vacant headspace. (The HOB would need to be adjustable.)

And you can reduce amount of water available to the return pump by simply removing some water from the sump ... as long as it doesn't cause your return pump to start drawing air.

That said, if your return chamber is really big (e.g. oversized for your tank), you may end up having too much volume in the return chamber to avoid overfilling the DT if the HOB pipe(s) become blocked.

If that's the case, the only other thing you can do is be sure to clean the U-tubes regularly to ensure no algae grows inside them. And check them regularly to make sure no air has slowly gotten trapped in them ... if there is you'll see an air bubble in the top of the clear U-tubes. The bigger the air bubble, the slower the siphon will be ... and the greater the chance the return pump will send water to the DT quicker than the HOB can drain it. THESE 2 MAINTENANCE steps should be done every month or two anyway.


As for whether or not to use both drains on the MD OF-1200, yes, BOTH DRAINS should be used at the same time. If you try closing off or blocking one of the drain pipes with a valve, the inverted U-tubes will pull water from the DT into the overflow box faster than the remaining drain pipe alone can drain it ... and the HOB box will overflow.

If you remove/shut-off both a U-tube and it's drain pipe ... leaving only one U-tube and one drain pipe in operation, then you will only be running the HOB at half-capacity and may not get enough turnover to adequately filter the water of a 150g.



As for adding a 'third' bean animal drain, that HOB doesn't have enough room to add an additional drain pipe. So, it wouldn't really be an option.


FWIW, I ran a Marine Depot Nano HOB on my 24g for four-and-a-half years without any issues whatsoever. They work great as long as you set 'em up right and clean them once in a while.

Wow. Thanks for the all the help!