The last time I successfully fixed this issue, I turned the shut-off valve fully in—then fully out. It sounded a bit "crunchy" as the valve closed off the water supply, but the water flowed once again.
I don't know what the offending substance was, but it wasn't due to well water—which I've never had. Piped-in water can carry small rust particles which can collect in places such
as small valves—a likely problem with Town water.
(This particular shutoff valve is the one located below the tank near the floor. My 53-year old place never had a shut-off valves, and consequently has never had a shut-off valve failure!)
Another valve—made of brass and located inside the tank—has never accounted for
slow filling. (But has made for some exciting water displays).
The
very last time I used this "quick-fix", the valve itself immediately started leaking.
Even then, if the leak is slow enough, a pan can be placed under that slow leak and the valve
can slowly seal itself.
I
love water, and even like plumbing.
