Open-loop water source heat pump valves keep failing. – GreenBuildingAdvisor

We have an open loop water source heat pump. Our water is pumped out of a well, circulates through the system, and is pumped out. The open and close valves that regulate the flow of water into the unit continue to fail. Often they either get stuck in the open position and don’t close or leak and flood the basement. We’ve changed three separate valves with seemingly  high quality replacements.  

One explanation  from our contractor was sand getting in the valves, but we put a sand filter in that’s clearly trapping the sand but the failure continued. The water quality of the water is acidic but the water source heat pump is supposed to be able to tolerate that. Any advice is greatly appreciated.