Washing machine will not drain. The drum will not spin. It make a loud whirring/grinding noise.

There is no obvious blockage and have checked the pump. The pump is working fine and the impeller spins.

Is this a blockage in the pipe or something else

If your washer doesn't spin or pump water out but the motor is running, your washer probably has a frozen pump pulley. If so, you need to replace the pump. To check the pulley, remove the pump from the washer and try to rotate the pulley manually. If it doesn't turn freely--if it's frozen or stiff--replace it.

Source: Repair Clinic (http://www.repairclinic.com/Washing-Machine-Troubleshooting?red=#itdoesntspinorpump)