I have 3 such valves in the line and none seem to be able to move past 10/4 oclock position and water remains on. Is there a way to adjust valve? Seems there is slot for screwdriver in center of valve.
I'm trying to understand what kind of shut-off this is. Most PVC valves are 1/4 turn levers, or ball joints with a T shapped handle, in both cases, when the handle is perpendicular to the pipe, it is closed/off when it is parallel with the pipe it is open/on. Other valves like a brass cock will be a round handle that you turn clock-wise to close the valve and counter clock-wise to open it. These type will turn many full revolutions. If you can't move the valve, it may be that calcium deposit has glued the inner valve into position. You might want to lightly tap it on all sides with the handle of your screwdriver as you try to turn it. Don't put to much force on it though because you will likely break it. Don't waste your time trying to unscrew the handle, that won't make a difference...
Jeff B is right, the screw you see is for taking off the handle, nothing more. A quarter turn should do it. If it doesn't turn, lightly tap on it as you do.
The threads are stripped, you will have to get a new one, until then shut off main line into house if you are flooding
