return plumbing question
 

so i am toying with designing a few tanks for the future and am wondering about running the return below the water line.... do back flow preventers work well enough for this or am i going to flood my house????

my current system has the return over the top of the tank and i just have anti syphon holes drilled to keep it from back flowing.....

i am trying to design a gyre tank with about 140G (60x30x18) volume... i would like the return to be in the side panel aswell.... is this too much stress for the side panel? the tank will have a divider running about 75% of the lenth down the middle and a overflow at one end.. this will force the water to flow in a circular pattern.... overflow on one side of the divider and the return on the other... i cannot resize my "paint" drawing of it and i have to leave soon so i have no time to redraw... i will try to add a pic soon..

EDIT: should add this it to be a penninsula style tank..

would think be taking a chance with a check valve unless your sump was big enough.

Could do a CL for the gyre.

from what i have read the CL would be overkill... you dont need much flow as the water is always moving in one direction, and there should be nearly no dead spots.

If you look at my return line on my 50g build you will see near the overflow a black capped on a t. It has 2 lines on it that I hookbairline hose to and feed to the over flow when pump turns off air enters the return line so it won't syphon the whole tank. Since my return line enters below waterline

If you want pics I can take some tonight for you.and post

power head then

i am hoping to have no powerheads in this tank... the flow from the return should be enough. all the water in the display should move via the return and overflow so there should be no dead spots and a constant flow being what ever the return puts out... they water will start at the return and run down one side of the divider and around the end and back up the other side of the divider and into the overflow... each side of the the divider will have 15" of room for rock and fish etc...

thinking of adding a surge device to the return aswell.. anyone have any good links to making a surge??????

Lots of tanks have side and back return holes, typically you don't have to worry about creating weak points as they don't usually go at the weakest point of the tank.

A surge is a waste of time for a 140gal, once you hit 500+ it starts to make a little more sense.

I'm not sure how you plan on setting up a gyre flow pattern with the return, typically this is done with two closed loop systems each pushing and pulling in opposite directions of the tank so you run them on interval timers. This way you'll have flow pushing one direction for a period of time and then switch it to flow the other way. Also you can size a closed loop pump to pretty much any size you want so I fail to see how it would be overkill.

Why not just run a wave box? You could even build it externally to avoid seeing it within the display.

guess I've set mine up as a bit of a gyre with the CL/return/overflow but without the partition and with a bit of a surge from the OM (old pic here).