Thanks!

I dug up a couple of links while trying to educate myself. This one talks about the various water tests:

http://ga.water.usgs.gov/edu/characteristics.html

Sounds like water hardness would be another good one for build up problems. I've heard of it before and apparently not a problem in my area.

This one was also fairly interesting:
http://water.epa.gov/type/rsl/monitoring/vms59.cfm

This latter one does note that conductivity is only good for measuring inorganic solids, organic stuff like oils, etc would lower conductivity.

So if I'm getting this right...electrical conductivity is kind of like PH or water hardness...just one of many tests that are often done on water, but not really related at all to thermal performance.

I'm just slow, when I first saw the term conductivity, I thought "Thermal Conductivity" and more is better

I think I'm getting it slowly now..