Every time after toilet flushes and finishes filling up, there is a thump sound translated to the refrigerator through the water line (for water dispenser and ice). It generates enough vibration to rattle the bottle inside refrigerator. This happens to all the bathrooms. Our refrigerator is new and a new main ball valve along with pressure regulator was put on. Water pressure is set at 45PSI.

Was told that this may be a water hammer effect, and will require arrester to resolve this. But, reading the refrigerator maual, it promotes purging air bubble from refrigerator water line as it will lead to dripping. So, if air bubbles are to be eliminated, will arrester even works? Please advise the best way to fix this problem.

Some device on your plumbing system has loose part. Since it is happening every time toilet fills up, than it may be angle stop at the toilet. Go to the toilet, Close and Open angle stop. Also, it may be your pressure regulator gone bad. Go to the pressure regulator and move the adjusting bolt 1/2 turn in and back out. See if the noise continues...