My mother's house was built in the early 1950's. Most of the
electrical outlets are the original, two-prong outlets, though
a handful were replaced at some time(s) in the past by newer,
three-prong outlets.

I was checking the newer outlets recently with one of those
testers with three neon bulbs that light up in various combi-
nations depending on the circuit status, and most of the new
outlets were showing an "open ground".

I shut off power to one circuit and opened up the electrical
box containing one of these outlets to have a look, and I was
dismayed to discover that the ground screw on the outlet was
not connected to anything at all! However, even after I had
attached a ground wire to the box and to the ground screw on
the outlet, it didn't make any difference -- the tester still
showed an open ground.

My tentative conclusion, at this point, is that the boxes are
probably not grounded. Again, we're talking about early 50's
construction, so I assume grounding of electrical boxes was
simply not a standard practice required by the code when the
house was originally built.

Is it reasonable for me to conclude, at this point, that the
only safe way to get these outlets properly grounded would be
for an electrician to ground the electrical boxes?

This is a one-storey, ranch-style house in California with a
crawl space under the house (no basement). In general, should
I expect it to be possible for an electrician to do this job
by connecting a ground wire to each box, then routing all the
ground wires through the floor and grounding them all? Or is
the job likely to be more complicated than that?

Rich Wales http://www.richw.org