Clunk in water system (not a pipe hammer)

[CoveyLane]

We had our submersible pump replaced last year after about 34 years underground. Some time after that we have been hearing a loud clunk at times. Due to the pandemic it took quite awhile to get a plumber to come. They thought it was the check valve but replaced the pressure tank and switch along with it. Still had the clunk but was out nearly $500. Within a week the cut off on the switch cut out and we had no water. Plumber came and replaced pressure guage and adjusted. He was the boss so we felt confident everything was going to be working right. Still had the clunk and the pump was cutting out at 70 instead of 60. It was a 30-50 switch adjusted to 40-60. I tried adjusting the nut for the high side but could only get it down to 65. By that time the spring on that screw was floating (no pressure left in spring). I talked to the plumber. He didn't seem too concerned. I'm thinking of switching to a real 40-60 pressure switch. Any ideas about the clunk? I don't think i can attach the video of it.

 

[Bannerman]

A check-valve is located internal to the pump, but you said a plumber replaced it along with the pressure tank and switch. By this, it sounds as though there are 2-check valves installed, one of which is external located close to the pressure tank.

There should only be one check-valve installed which is the one in the pump. Having two check-valves installed will result in the noise you are hearing and will cause problems if permitted to continue.

Here are a few of many relavent threads which Valveman discusses issues with multiple check-valves:

https://terrylove.com/forums/index.php?threads/pressure-tank-hammer.77689/

https://terrylove.com/forums/index....e-tank-and-have-a-few-stupid-questions.88227/