Clunking sound when ground water heat pump stops running
Could be a loose mounting bolt on the compressor, or the other common noise a heatpump makes that concerns people is the reversing valve shifting. This changes the direction of high pressure refrigerant, and low pressure refrigerant. Causing line sets to hammer, if not properly secured. If sound is loud check the supports on the line sets (copper lines from outside to inside assuming it is a split system.)