I have a leaky cold water valve in my laundry room. It is a gate valve with a similar set up to This post (although older and with a lot of scaling). I did some research and decided to buy some 5/32 inch valve packing to re-pack the valve. I cleaned the old packing out, scraped the scaling off of the nut, wrapped the packing around the stem 2 times and tightened the nut down until it stopped leaking. I then decided to test it with a load of laundry. Of course, at this point it started leaking slowly again.
This has led me to a question which I haven't been able to find the answer to online:
The valve leaked whether it was open, closed or somewhere in between. Does this suggest that the issue is related to the washer or o-ring located at the bottom of the stem rather than the packing nut itself?
I'd hate to call a plumber, only to learn that I hadn't packed the nut properly but replacing the stem is above my pay grade. Any input is greatly appreciated!