Originally Posted by mastershake93
i have a cpr backpack protien skimmer, and i was wondering that if i drilled a hole just under the origanal exit, and ran my plumming down to my sump whould work. i would have a slightly larger return pump to compensate for pumping up to my tank
Your CPR backpack has an impeller that pulls the water out of the tank, right? If you don't match your return rate exactly
to your overflow rate, you will have a flood. And it will be impossible to do that, considering that a pump can lose or gain flow over the course of an hour/day/week...you get the idea. If your return pump is pumping at 600 gph and you have to compensate for 3' of head (say -50gph), then you would have to pump 550 gph out
of the tank. If you are pumping 525 out of the tank than over the course of an hour, you will pump 25 gallons more into the display in one hour. Imagine what will happen in five! Another scenario is you have matched the return to overflow perfectly. Then some algae gets caught in the impeller of the return pump, slowing down the flow to 500 gph. Now over the course of one hour, 50 gallons will be pumped out of the tank onto your floor.
The idea of that onefish is promoting is simple: gravity controls the overflow. Water is pumped into the display, and flows over a baffle and the drain is gravity fed. Therefore only water pumped into the display can flow over the baffle. If your return pump malfunctions, then water will stop being pumped into the tank and cannot flow over the baffles.
With a drilled aquarium, you do not have to worry about a siphon break. That makes this the best option. If you have a power outage, water will stop being pumped into the aquarium (the reverse action of the return pump in a power outage will cause water to be siphoned the other way, so be careful of that) and no water can flow over the baffle. With a Siphoned Overflow when water flows over the baffle, it is then siphoned over the aquairum wall and flows down into the sump. When power goes out, that siphon is broken and needs to be restarted when the flow starts again. There are continuous models on the market, like the CPR CS series
, which use an air-lifter pump to restart the siphon in the case of a power-outage. I have also seen DIY versions of this just surfing the net.