Plumbing Questions? Ask a Plumbing Expert.
there are a few ways
if the house is old some plumbers back in the day installed air hammers i would try this first old or new house
turn off the water and drain the house compleatly this will drain the water from the lowest point this will drain the hammers and restor the system
thats one thing
the next is installing a air arester by the water main this will absorb most if not all of most pipe knocking
the other method is to locate the cause of the knock ie; a toilet a washing machine or some mechanical valve found on a washing machine refrigator ice or water maker some times thease valves may need replacement and can also cause a knock