Loud knocking sounds- plumber says no leaking in old section- newer sunroom- perhaps there- how to find out- must rip up new floor to get under sunroom

Bleed air out of system. Then check to make sure system holds the water pressure it is designed for. You can use a special tool to check for leaks without tearing up the floor. Most companys do not have this electronic tool. You will have to call around to find a company that has one.