In doing a first test for CH using a TF100, I was getting a "fading endpoint". According to the extended instructions, this is caused by interfernce from metal ions in the water. I was able to complete the test by adding five drops of R-0012 at the beginning per the instructions (result was 90).
Are the metal ions something I should be concerned about or somehow test for?
Is the likely source of the metal from my fill water (which is city water)?
When I do my next drain/refill should I use one of the fill filters (such as the Pre Fresh) that are supposed to remove (at least some) metals from the water?