Thanks everyone who suggested I check the packing nuts on my valves to see if they need tightening. This is now the first thing I will try, but please know I have never found one of these nuts loose anywhere. Right now I am assuming they are tight and it's just that fresh packing must be put in. I wish someone had directed me to a comprehensive discussion of valve packing, particularly which color string to use--the white (is that teflon?) or the black (graphite?)--but I guess even how much to use and such esoterica as do I wind it clockwise or counter-clockwise will be left to me to figure out! And I badly need to be told why the literature says DON'T re-use old compression nuts and rings with new valves, while everyone else says to DO it, and both sides are adamant. And FYI to those who took me to task for not mentioning the packing in the beginning, I did mention it in both my postings in this forum--How to fix leaking angle stops, and Removing escutcheon plates--and it was late in my second posting that I made my second mention but it was there nevertheless. In fact fear of omission is why I write at length, something else for which I get criticized.



Edited 3 times.

The packing nuts ARE "tight" but the packing itself has "loosened" around the stem, due to the movement of the stem as it is opened and closed.

Turn the valve handle so that the valve is neither fully open nor fully closed. Use an adjustable wrench on the valve to steady it and another adjustable wrench on the packing nut, if you turn the nut 1/8 of a turn the leak will most likely stop.