I purchased a new gadget:
Amazon.com: HM Digital TDS-EZ Meter/Tester, Water/ppm/Purity/Filter: Home & Kitchen
Some of you may have heard that Texas has been in a drought. One side effect of very limited rainfall is the fact the water in our underground aquifer - located in a limestone karst formation - gets progressively harder over time. With almost no new inflow to the aquifer, calcium carbonate levels in the water become increasingly concentrated and the hardness level goes up - way up.
I replaced our water softener just prior to retiring seven years ago. It has done a good job for us until this year when water drying on the kitchen counter or in the dish drainer began leaving a distinct white residue. I went though the softener's troubleshooting and maintenance manual and cleaned out all the gunk in the controls and valves, but no improvement. The water doesn't feel super hard when I shower, but I know something isn't working like it should.
As a frame of reference, I had the well water tested after we moved in and it showed 750 ppm. I believe the EPA considers over 500 ppm "contaminated". This is why we don't drink our well water.
Tests of three different water samples with my new toy:
16 ppm - "Fill it yourself" bottled Culligan water
137 ppm - tap water after passing through the softener
910 ppm - untreated well water
Question answered - the softener is definitely working, but the level of dissolved solids is beyond the capability of the softener. The solution is to either buy a higher capacity softener or wait for rain.
I'm a patient man...