top off on a nano

[Rippin]

Here's a link to the instruction sheet:
http://www.aqua-medic.com/products/d...mp_SP_3000.pdf

The check valve is blue and looks like any other in-line check valve that you can get at a fish store. If you don't have it already installed in-line between the pump and the tank then you probably don't have one; therefore the valve installation is not the problem. Does the pump work if the head height is reduced?

If the pump hose (white one) is not properly greased it will not work properly. Grease should have been included in the box when originally purchased. Any thick silicone grease without any petroleum distillates or solvents will do the job.