Overflow box help please.

[TimeConsumer]

With proper sump design you can eliminate the flood issue if your siphon fails. My return area of my sump holds a mere 3.75 gallons. My DT has 1" room at the top for extra water, which is exactly 3.75 gallons. So if my siphon fails, my return pump will fill the tank with about 3 gallons of water (the bottom inches of the return area are below the pump inlet) and my DT won't overflow onto my floor. Yay! This design will not work with an ATO unless you have float valves in the display (and you trust them). There are obvious drawbacks, 3.75g is a very small return area, you don't want to miss a day of topping off. And even if there's a failure, you may not flood, but you still lose a pump.

This can work with your CPR, but my Lifereef helps me sleep at night.

 

[~RuSh~]

With proper sump design you can eliminate the flood issue if your siphon fails. My return area of my sump holds a mere 3.75 gallons. My DT has 1" room at the top for extra water, which is exactly 3.75 gallons. So if my siphon fails, my return pump will fill the tank with about 3 gallons of water (the bottom inches of the return area are below the pump inlet) and my DT won't overflow onto my floor. Yay! This design will not work with an ATO unless you have float valves in the display (and you trust them). There are obvious drawbacks, 3.75g is a very small return area, you don't want to miss a day of topping off. And even if there's a failure, you may not flood, but you still lose a pump.

This can work with your CPR, but my Lifereef helps me sleep at night.

This is exactly the method that I used. My last chamber has eggcrate 6 inches up off the bottom of the tank holding up my return pump. If my overflow loses siphon, the pump will empty water from the last chamber, but only about 3 inches total (I run the water about 1 inch over the return pump, and the pump is 2 inches tall). With 1-1.25 inches of space in my display tank I have roughly 1.5 gallons of space. I've broken the siphon on the overflow a handful of times to test this and it stops pumping water into the display with plenty of room to spare.

Thanks for the help.