Water needs to be introduced into the suction line before starting the EXT pump for the first time. The EXT Pump Plumbing Kit includes a plumbing tee with a threaded cap on the discharge side that is used as a priming port to add water to the suction line. Close the ball valve (turn valve perpendicular to PVC pipe) when filling to make sure the water being added fills the pump volute and suction line. The EXT Pump Plumbing Kit includes a 3″ swing check valve located beneath the surface of the water. This check valve holds the water in the suction pipe. Once filled the threaded cap can be replaced back onto the tee and the pump can be powered on. The ball valve can then be opened to allow the flow of water to begin. Once primed, the pump can be turned on and off without priming as long as water remains in the suction line.
Note: If the initial attempt to prime the pump fails, you must turn off the pump and allow it to cool down for a few minutes before attempting to prime again. This prevents the risk of damaging the mechanical seals through thermal shock during another priming attempt (suddenly introducing cold water to the warm mechanical seal surface).
Click here for more information on the Aquascape line of EXT Pumps