Tell me again why I can't use a return for my closed loop intake?

[NoSchwag]

Can someone tell me again why I can't use one of my 2 corner returns as a closed loop? I've read it somewhere but I can't find it.

I'm not worried about flow from the 1 return that I'll have left because only 300 gph is going thru my sump. Plus, it's not my main means of flow.

Thanks.

[BeanAnimal]

The pump will suck the return dry. Its kinda that simple (well ok not really).


The closed loop pump will overpower the return pump and the other overflow will run dry, or the closed loop overlfow will suck air. There is no easy way to balance the flow. If the water overflows to fast into the sump it will overlfow...

You get the idea... to many variables.

[artis]

Actually, I do this in a roundabout way. I use my sump as a source for the loop and the sump is fed by the return. To be blunt, the return simply does not provide enough flow to feed the loop and provide the sort of turnover one seeks for flow. In my 55, I suspect I'm lucky to see 500 gallon flow in this fashion and in truth its likely less. The overflow is designed for a max of 600.

I would not build things this way again, if I had it over. Likely I'll add a tunze or something to get the flow up after awhile.

[NoSchwag]

Originally posted by BeanAnimal
The pump will suck the return dry. Its kinda that simple (well ok not really).


The closed loop pump will overpower the return pump and the other overflow will run dry, or the closed loop overlfow will suck air. There is no easy way to balance the flow. If the water overflows to fast into the sump it will overlfow...

You get the idea... to many variables.

Thats what I figured.

But then I can't help think that you would just be pumping all of the water that you sucked out of the overflow, right back into the tank.

I guess I thought that you would just have to compensate for that extra water that the closed loop uses.