Hank
I tried the foam insulation idea and found it helped a bit, but anything that fastens the pump to a sounding board i.e. sheet of plywood with screws will transmit sound and the bubble mounts worked better. I will be interested in seeing how much replacing the PEX with hose makes and my expectation is that it will help some. Most RV pumps use a diaphragm positive displacement pump which will means, it will pulse but it can run dry with out harm. In looking for a non diaphragm pump I am so far not finding anything.