Fresh water pump

You are probably correct that it seems like there is air in the FW system which is making the noise and vibration. Normally to vent the system turn on the tap with is lowest in the system then turn it off. Keep turning taps that are higher up on and let it run for a while then turn off. Once you get to the highest and further away from the pump the system should be fully purged of air. You should see some "sputtering" of air and water at least at some of the taps. If this doesn't stop the problem there may be a problem with the pump - try fitting a new pump. Generally these pumps are not serviceable. The other cause could be a damaged hose between the pump and the water tank which is allowing air to enter the system.