Please find included two pumps which have been built specifically for the purpose of flushing a pipeline.
Each pump will need assembly with included outlet nozzle Item 1 and suction strainer Item 2 so the pump looks like this
Fig 1. You can mount the outlet nozzle in which ever orientation suits your situation. Pump mounting brackets are also supplied.
The check valve Item 3 on the case drain is 100 psi and designed to counter act the high water pump pressures and prevent shaft seal failure. DO NOT remove this check valve. Simply connect case drain hose to the outlet fitting of this check valve and run case drain hose to tank as per normal.