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View Full Version : bottom vs back internal overflow?


Johnb123
02/05/2016, 02:03 AM
is it just the size difference? is there noise or performance difference too?

RocketEngineer
02/05/2016, 07:43 AM
Most bottom drilled overflows have a very short weir length where as a back drilled overflow will be much longer. The longer weir allows for more surface renewal which is the main point of an overflow.

Also, the bottom drilled boxes are normally quite large and take up space on the bottom of the tank that could be used for LR or corals. Another issue is the settling of detritus next to the box which doesn't happen in a back drilled overflow as the water can move unimpeeded under the overflow behind the rocks.

EvenFurther
02/05/2016, 07:44 AM
Back internal/external gives you more floor space for aquascaping. Some tanks have tempered bottom glass, and you can only drill the back glass. A bottom drilled doesn't require so much clearance behind the tank. Noise/performance would depend how the drain is plumbed in the overflow. You can set up different drain methods regardless of where the tank is drilled. You just need the right number of holes, sized correctly. If you want the best, or ideal surface skimming, you want a long weir like a coast 2 coast.

Bottom line is you can create an awesome tank either way.

Johnb123
02/05/2016, 09:05 AM
what's a weir is it the overflow teeth? also i'm talking about all things being the same ie. hole sizes and number of holes. so there's no difference in noise or performance?

Drae
02/05/2016, 10:22 AM
Reef savvy ghost. Done deal imo.

JaySchulz
02/05/2016, 10:29 AM
Another benefit to the back internal/external overflow other than what has been already posted above is in the unfortunate need for servicing the bulkhead, piping, or the actual overflow box, you would only need to drain a few inches of water to work on these items dry.

EvenFurther
02/05/2016, 10:32 AM
The weir is what the water flows over, could be a straight glass edge, could be teeth.

azjohnny
02/05/2016, 04:04 PM
My next tank will be a back over flow

Johnb123
02/05/2016, 05:50 PM
I initially came into this hobby with people telling me the bottom overflow was better guess they're wrong?

EvenFurther
02/05/2016, 06:25 PM
I would look at this way, "better" is a long weir for optimal surface skimming. Combined that with a fail safe drain set-up that operates quietly. I wouldn't be caught up on what panel the overflow is attached too, or what panel the drain holes are in. Someone could set up a "back internal overflow" that works poorly or is loud. A coast 2 coast or near C2C with a 3 pipe bean animal drain is an awesome set-up. And it works perfect thru a back non-tempered panel.

Keep in mind some things are better suited for certain tanks sizes/shapes/tank placement in a room. Smaller pico/nano tanks can be beautiful without much fuss over the overflow location.

Manfredo
02/05/2016, 10:51 PM
Reef savvy ghost. Done deal imo.

+1 - This is what I have an it's awesome...