Hi!
One of our cold water shutoff valves started to leak for no reason. The leak is not at the glued joints, but under/around the turn handle. When I turned the handle, the valve seemed like it was not open all the way, and when it fully opened, the leak stopped. This valve has not been opened/closed in years. What would make it start to leak out of the blue? We discovered this leak within a few hours, and it caused some damage to the ceiling below. I shudder to think what would have happened if we had been gone for several days! Can I just replace the washer to fix this problem? Also, do I now have to be distrustful of all the other shut-off valves in the house? Any advice will be appreciated!
Thanks!

Can I just replace the washer to fix this problem? Also, do I now have to be distrustful of all the other shut-off valves in the house? Any advice will be appreciated!
No! This is a bonnet packing leak and it's real easy to fix. Open the valve up so that the stem starts to leak. Now snug up the bonnet packing nut located just under the handle until the drip stops. STOP! Do not over tighten. This shoulkd take care of your leak. Good luck, Tom

No! This is a bonnet packing leak and it's real easy to fix. Open the valve up so that the stem starts to leak. Now snug up the bonnet packing nut located just under the handle until the drip stops. STOP!! Do not over tighten. this shoulkd take care of your leak. good luck, Tom

I forgot to mention that this shut-off valve is plastic, not copper. Does that make a difference?
Thanks!