I use these for well pump tests. It is useful over time as the well
is pumped hard enough to draw down to see changes in concentration
of dissolved solids, temperature, and PH. It tells you generally
if the geology is such that increased use will produce less or
more stuff in the water.

If the water looks to be at reasonable levels of TDS etc, then
samples are sent to the lab for exact findings. These tests can
cost upwards of $4000 for drinking water quality.

SO--- these tools are interesting, but not very useful for the
lay person.