A shut-off valve stops hot or cold water from travelling to a certain point in a building. Plumbers refer to this valve as a "gate valve" or "globe valve." They consider it "frozen" when it refuses to turn to the left or right with normal hand pressure. Do not try to force the valve, as that could damage the valve and other pipe fittings. Repair the valve as soon as you can to prevent a serious leak. This is an easy maintenance job that involves using a few basic household tools.
Locate the valve that controls the flow of water to the stuck shut-off valve. Turn it to the "off" position. You can shut off hot water at the hot water tank and cold water at the shut-off near the water meter.
Tap on the shutoff valve body with the handle of an adjustable wrench. Try to turn the valve handle clockwise with your hand.
Loosen the packing nut of the shutoff valve with an adjustable wrench. Tighten the nut when it begins to leak water. Try the handle again.
Remove the valve handle. Use a screwdriver to remove the screw that holds the handle in place. Lift the handle off and set it aside with the screw.
Soak the groove around the base of the handle stem with penetrating lubricant. Wait 15 minutes for the lubricant to penetrate.
Grasp the handle stem with locking pliers and apply gentle pressure while turning it clockwise. If the handle stem fails to loosen, turn it slightly in the opposite direction. Apply more penetrating oil and repeat the process with the pliers.
Label water pipes and other lines to show what they carry and to which destination.
Be careful when attempting to free a stuck water valve shut-off. Copper pipes and brass fittings may crack or rupture if you strike them with a heavy hammer.