Aquamist pump won't prime

[Giles Gilbert]

Hi Folks,
I need your help. The water level in my tank is above the pump. I've sucked water all the way through the pump supply pipe such that it now continues to flow out of the end of the pipe that is connected to the pump. I power on the pump but the water does not get sucked through! Even if I disconnect the pipe on the exit side of the pump nothing comes through. I've even tried sucking on a pipe connected to the exit of the pump while the pump is running and all I get is a vacuum in the pipe I am using to suck through. What am I doing wrong folks :-(