Met with Greg, had a brief conversation regarding the issue. I suggested to purge the lines and Greg agreed. Set up the hose and bled all five zones with Greg present. No air bubbles were apparent in the zones. I performed a visual inspection and the boiler was not properly plumbed in the riser of the boiler leading through the air vent station. I discussed several contributing factors, regarding piping banging with restrictions. Greg was satisfied with the service.