What kind of waterers did you install? I am getting ready to put in a single ritchie unit. I have about 350 ft of 1.5 inch, tapped between the well and tank out to a frost-free. I am planning to tee off of that line, reduce to size, and install the shut off valve. I have had no problem with the frost free fixture provinding any issues, nor have I had any issues with hammering at the well tank.
I guess I am wondering if I need to install one of these...
I installed Drinking Posts, I posted this thread on it last fall.
You won't have hammer with a manually operated valve because it closes so slowly (relatively speaking). I'm not familiar with Ritchie units, but if it has a spring or solenoid operated valve, you'll need an arrestor. The issue is how fast the valve closes: if it closes really fast then it creates a shock wave that causes the hammering. If you're T'ing off an existing line, I'd put one larger arrestor at the end of your longest run, and a smaller arrestor at the end of the run for the waterer. The issue is that the column of water moving down that long length of pipe has to stop suddenly so the best place to absorb that shock is at the end of the long run. If you can't get to the end of the longer run, just put a large one by the arrestor and hope that does the trick. I chose to put in two instead of one because they're cheap compared to the labor of digging the whole thing up if one fails.