hang on overflow... diagram--work of flood?

[joseph mcdonald]

i have a 20 gallon tank, want to build some sort of under tank filtration to avoid a problem i've been having with fish and anemone gettin stuck to intakes of filters (crazy aquatic things)...

this is my idea.. its not exactly to scale may vary when built.. hope to use 1" flexible tubing down to sump, then have all filtration done there, and pumped back by a 150gph+ (@ 4ft), through flexible tubing with a check valve in the return flow...

 

[mr . salty]

Looks like just about every other overflow I have ever seen....Should work...

 

[broomer5]

As the water falls through the teeth of the inner box, it must fall over these teeth and the level in this inner box must be below the water level in the main tank.
Then on the outer box, if you were to install a 1" bulkhead fitting, and have a riser in the outer box coming up from this bulkhead fitting, that rises vertical and stops somewhere below the level in the inner box - it should work.
Some people will make a seperate chamber in the outer box to acomplish the same thing, but top edge of this wall must also be lower than the inner box water level for it to work flawlessly.
The water will enter the inner box through the teeth, fall through the teeth to a lower level than the display tank, up and over the U-Tube siphon, into the outer box, will rise to the level of the little riser/standpipe ( or wall top ) and spill over into the drain.
Anything other than this will most likely give you problems.
I like your drawing by the way Joseph, with a few minor modifications I'd say you've just about got it !
I can email you a good schematic/drawing of a really nice overflow - but hesitate to do so here
Edit:
Sorry Salty - I was typing reply as you were replying.

 

[joseph mcdonald]

Thanks for the info.. any schematics would be helpful, just never really thought about how these work and drilling isn't an option...
i have a spare 20gal tall which i'd probably put 15-20 gallons in...... i've gotta figure out what to put in it... i'm thinking in the overflow system maintaining tank water level isn't as difficult either?

 

[joseph mcdonald]

slighty altered to save space...
and btw, ideas for a cheap return pump?

 

[bingo]

The only thing wrong in your diagram is that the water level in the outer box NEEDS to be lower than the water level in the inner box for the siphon to work. If you make that pipe that goes down to your sump as high as what you want the water level to be in the tank, you will have a flood. Either lower that tube to a little bit above the lower point of the U-tube in the outer box, or make a small overflow of that height like a Lifereef. If you think about it and build it right, the siphon will work fast, and not break in a power outage. Hope this helps and make sense. Good luck...

 

[mr . salty]

You should also incorperate some way to adjust the water level in the tank.As it is in your drawing,there is no adjustment,and the actual water level WILL be lower than in your drawing.You either need to raise the whole assembly up and down,or split the inner box from the outer box,and have only the inner box adjustable...

 

[mr . salty]

Maybe put a couple thumb screws in the "saddle" between the two boxes.Then as you screw them in,they press down on the tank's rim and raise the entire assembly...