Water hammer arrestor placement
Put them near the sink.
Water hammer is caused by the inertia of the moving water in the water lines trying to keep moving when a valve shuts it off suddenly - so placing them at the far end of lines is most effective.
In &quot;typical&quot; bathroom fixtures of the current era, the sink is also the most likely to be a &quot;quick&quot; shutoff (which is the most prone to causing water hammer.) Valves that shut more slowly allow the water to slow down as the valve is closing, whereas those that close quickly get to all the way shut while the water in the pipes is still moving.