Probably a stupid questions but here goes...

I've never seen a in tank overflow working in person or how the plumbing works.

So, let's see how close to figured out I have this.

Water is pumped in from the sump which would raise the water level causing it to flow in to the over flow. In the bottom of the overflow is a bulkhead that is affixed to a pipe that then drains the overflow back in to the sump through a filter sock of some sort at the end of the pipe.

The returns for the sump should they "ideally" be above water level then piped down in to the water using some sort of ball lock tube sort of like a powerhead?

I was thinking then do I need a sort of float valve for a shut off if for some reason the water level was to drop too far in the sump if for some reason the overflow stopped working?

Do I have this about right in my head?

 

In principle yes

you do want a device like a float switch that turns of the pump, should the overflow be blocked and water not coming back to sump

your set up should be able to accomodate all the water in the pipework, should the pump stop working, and all water drains back to sump

and your float switch should be set, so that it only allows water back into tank to the capacity ?( above the overflow, but not above the rim of the tank)

Steve

 

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Thanks for affirming my thoughts!