DetailsC Style Self Piercing Tap Valve With 1/4" Comp - Used on copper lines. Make sure to install it inline after the cold water shut off valve. Mount and tighten the self piercing valve on the copper line in a easy to reach place. Turn the piecring needle clockwise all the way in. This drives the sharp end of the metal needle into the copper tubing and will pierce a tiny hole. This is the "OFF" position for your new RO system. Turn counter-clockwise to open and turn on.