Toilets, Sinks, Showers, Tubs and Disposals - Toilet Water Shut-Off

Last time I changed the valve in my toilet tank, I easily shut off the water by turning the water valve to the tank. Lately I've noticed that the toilet is very loud when filling after a flush, and I thought I should try installing a new fill valve, but the water doesn't shut off. It's not even going down to a trickle. It's still a full flow of water even when I turn the valve all the way in the off direction. The house is only 14 years old, so it's not an old, rusty pipe. Should I try a wrench? I was afraid of breaking something.

The supply valve has gone bad and needs to be replaced.If it's original to the house and is 14 years old then it's guts are plastic and it's age is average lieftime for one of these valves.Attempting to tighten with tools will just break it more than it already is and might ring off the stem.Also these valves are not designed to be repaired so determine whether it is soldered on or screwed on and it's size where it attaches to your plumbing and go from there.Use care in removing if you get resistance as they can become locked on from over tightening or mineral deposits and corrosion.

The washer inside the valve has probably disintegrated and needs replacement. The only problem is most of theses valves have a push on washer and are not really meant to be repaired as spdavid has mentioned. You will probably need to shut off the main water supply in the basement and replace the valve.