I noticed a little chalking on my gray truck after going through my automatic. I reuse my reject water for HP rinsing followed by SP rinse. I checked the hardness of my water and it was at 3 grains. I then checked it on my HP rinse tank that was full of reject water and it was 9. Can someone explain this to me? Makes me wonder if I should quit using my reject water and rinse with softened city water only.