Clunking sound when ground water heat pump stops running

Question

This clunking sound is one loud sound followed by a few smaller clunks. It seems to be coming from the water supply pvc pipe that supplies water to the heat pump in the basement. The sound starts near the heat pump and runs back towards the bladder tank 25 feet away where the water supply enters the basement. A 1/2 hp submersible pump supplies the water from a depth of about 40 feet. I have secured the supply pipe to the floor joists, but the noises persists. This system is almost 20 years old. It has only been making loud noises the last couple weeks.

Could this be caused by air trapped in the pipe? If so, what is the remedy? Thanks

Answer 1

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.)