Thank you for your replies. I will contact my HVAC guy and hopefully he can solve this issue. The problem I have is that the basement is finished and the ceiling is drywalled.
Everytime the new power vented gas water heater cycles on, there is a knocking/clicking sound that comes up every four seconds or so which appears to be coming from the 3" PVC exhaust pipe from the water heater to the outside. I am guessing the hot air is expanding the pipe, but I don't know...