How else can we empty the tank?
A photo of the valve assembly above the pump would help but often you will find there is a standard 3" Bayonet type fitting there.. Now this is GOING TO BE MESSY so get a bucket in posiotion.. You will close the dump valve. this is important (NOTE: If you just turned on the pump and did not open the valve.. that's your problem) And wearing gloves (Latex, nitril or Rubber) and taking care cause there is going to be a mess, The king you need bleach to clean up, Disconnect the 3" inlet hose to the maceratgor.. use a standard 3" stinky Slinkey to dump. YOu may then remove, steam clean and repair the pump.