Sump on a small Tank

[RUFF]

Hi. Great group!
One year ago after much deliberation I started my small but successful FOWLR. tank.

[RUFF]

I am planning on adding a sump in basement directly below tank. I am thinking of a 40 gal Breeder tank with a refug. at one end an return area in middle. My fear is overflooding display tank,as I will be using a hob overflow and the sump is much larger than display.Has anyone used a water level in to shut off ret pump .(pump would run with switch n/c. I am also not sure what pump to use yet,I am used to gpm not gph. I will be feeding refug. with ret pump also. thanks

[javajaws]

You don't need to worry about the water level in the sump (so long as it doesn't run dry, etc).

What you need to worry about is that the drain to the sump from the tank can drain more than the return pump can pump back to the tank. The water level in the sump should remain relatively constant (and you can monitor it to determine if you need to add freshwater for evaporation, etc.)

So long as that happens and so long as you use an overflow box you won't have problems.

[RUFF]

thankyou for your reply,what I am concerned with is should the siphon be lost,in the overflow, the return pump will flood display. I have heard this has happened in much larger tanks.I'll use a 1" overflow and will be able to throttle ret pump,(by pass to refug.)
I will have 8.5' tdh loss.and am thinking of using a quier one 3000 pump. That should allow 200gph to display and the rest to refuge. I think.

[javajaws]

Well, If you lose siphon, you're SOL unless you detect the dropping water level in the sump and shut off the return pump. That's why people get their tanks drilled.

The problem with monitoring the sump level is knowing why the sump is low: loss of siphon or evaporation? If you use a dosing pump to replace evaporation you could probably monitor the water level fairly reliably (assuming you won't have "waves" in the sump compartment that the float valve is in).