arrestor

There is one toilet in my house that causes severe water hammer when it fishes filling. It is the last fixture on the line. The toilet before it has a slight bit of hammer, more of a tick than a bang. I am making sure the pipes are properly supported and am also installing a water hammer...

Should I put a water Arrestor on both the inlet and outlet of a water heater? it seems that just the cold feed line is making the noise and shaking but was unsure if I need to put one on each line. Also the cold feed to the water heater has a ball valve to cut on/off water to the water heater...