[jnaas2]

At what pressure does your pump turn on and at what pressure does it shut off at. And If they put a tee in the water line out side before it enters the house and connects to the pressure tank that could cause water hammer in the line just from the water going out to the tee and then when the pump comes on it reverses direction back to the pressure tank. A quick closing valve like the kind on a washer will also cause water hammer and you will probably need to install an arrestor on the washing machine cold water line to help stop the water hammer