wrote:
Thanks Jimmie...Google search brought me here. After dealing with water
hammer in one bathroom faucet for over a year, I just realized the valve
was only on about a quarter turn. With it all the way open/on, problem solved.

Depending on the type of valve in question, if you have opened it all the
way, you should now close it about 1/8 of a turn, maybe less.

You want to have some play in both directions. If the valve is fully open
up against the stop and it jams up due to corrosion, you may have trouble
closing it. The best practice is to open a valve all the way and then close
it slightly, maybe 1/8 of it's full travel, to ensure a little play to the
open side.

This applies to most gate valves and angle stops, not necessarily ball
valves.