ok it won't work then i guess lol. i'd rather just order a unit and pay a bit more than build one.

how about this one? http://www.marinedepot.com/md_viewIt...product=TZ4111

nope, same problem only worse. And Yikes! did you see the price of that? You are paying alot for optical sensors and dosing pump.

Think simpler. A quick google search turned up this for tank mount:
http://autotopoff.com/products/ST1/index.htm
or this for sump mount:
http://autotopoff.com/products/SS1/index.htm

to prevent cycling you can add the $20 reset switch upgrade. Highly recommended

Go
 

On another tack...
Have you considered mounting your return pump intake closer to the surface of the sump waterline?
When I built my 75G. tank I calculated 1 1/2" of space between my overflow and the top of the tank. That equals 5.5G.'s before it over flows. In my sump I calculated that 2" of water equaled 5.5G.'s so I set my pump intake at 2" below the sump water line.
If the overflow plugs the return pump will run dry before it floods the tank.
There is a trade off between flooding the floor and burning out the pump but the water damage from a leak on the 2nd floor outweighs the cost of the pump.
________
F11

there's water damage in the basement from it. it floods in the rooms upstairs and then comes and floods my daughters room downstairs.

I plan on simply using 2 HOB overflows - a Lifereef and a cheaper Hurricane as a "backup" (although both will end up flowing about equal amounts).

I'll be using an Eheim 1260 as a return (~450 gph at a 4' head) so either overflow can handle the load even if the other is completely shut-down (Lifereef 600 gph max flow, Hurricane 500 gph max flow).

Both overflows are the more reliable u-tube design and since I picked both up used, cost is very reasonable for the resultant peace of mind.

thats a great idea. thanks