I have a horrible water hammer noise when my sump pump shuts ff. It is an 8 ft rise and 30 ft run outside 1 1/2 pvc. I have tried repositioning the check valve from the horizontal run coming out of the pit to the vertical run, up the wall. I have tried putting the check valve closer to the pump and at the farthest point. I have tried a different check valve. I have tried two check valves. I even tried a pvc y above the check valve to an air chamber or capped length of pvc to act as a water hammer arrestor. I was going to try to put a small 3/4 inch spring loaded check valve just outside the foundation Y'ed into the 1 1/2 inch pvc to allow a vacuum break. Any other suggestions would greatly be appreciated Adam