To test water hardness before/after the water softener, one just buys the tester that REW just told us about.
I have to confess one of the readings I posted
here was incorrect. Turns out the post water softener 137 display had a small blinking "x10" in the upper corner of the display that I didn't see. Yep, the unsoftened water read 910 ppm and the 'softened' water read 1,370 ppm.
After a little googling I learned the ion exchange process results in an increase in particulate matter by approximately 20%. Why were my readings 50% higher? Turns out something in the softener was malfunctioning and the 'softened' water contained dissolved salt (not enough to taste, but when evaporated the water left a powdery residue with a salty taste). My earlier diagnosis that the softener was working correctly was wrong.
I went through all the troubleshooting procedures in the manual, cleaned out the venturi, made sure the drain lines weren't clogged, and checked out all the other "user serviceable" components without success. It suspected the final rinse in the regen cycle wasn't working properly, but any salt left in the resin tank should wash out after a short period of use. Since the 1,370 reading didn't decrease after a day of normal use, that ruled out a failed rinse cycle. I gave up.
Like Walt, I bought and installed a new softener. The old one, like my previous unit, lasted seven years.
If anyone is still reading, the test of the water coming out of the new softener is 190 ppm lower. I suppose that was the salt level the old softener was leaving (injecting?) in the water.
I hate plumbing work...