help with overflow

I am helping my neighbor with her tank she doesnt really know that much about it and either do i. I have a tank as well but my tank is drilled, her tank is not drilled. I am very unfamiliar with tanks with an overflow on them. My question is how do i get her tanks overflow to start running. The main tank starts to overflow everytime you turn the main pump on. There is no pump connected to the overflow and thats the way she said it has been forever? I AM AT A TOTAL LOSS.

 

what kind of overflow is it?

 

I may be wrong but, usually there is a little hose that is stuck in the overflow then into the u tube and when you suck in air from the hose it creates a siphon.

 

Pics would help greatly. There is an overflow that just works on siphon/gravity. My friend has it. But in the case of a "power out" the siphon won't start on its own. The CPS that uses the pump will.
Does it look like a tube going from the tank into the overflow?

This needs a pump:
CPR Overflow Box

This does not:
Over Flow Box <br> 10-75 Gallon Single <br> By Eshopps

 

4Phish has got it.. Stick an air line up in to the U tube that is in the over flow.. Position the hose so the end of it is at the top of the U. Once there start to suck out the air and the siphon will start.. repeat with the second U tube if there is one. If there is a power outage those tube should not drain.. When the power comes back on the siphon should start again automaticly..

 

you will need to make sure there is water in the overflow box outside the tank for the siphon to occur also.