"Do I need a water softener?
No. Water is considered "soft" if it has a hardness value of less than 50 parts per million (ppm). Our tap water has a hardness value of approximately 40 ppm (milligrams per liter) or 2.5 grains of hardness."
This is on the FAQ page for my local water utility. Would you use this water to water CP. I thought I read somewhere where water under 50ppm is sufficiently pure for use with CP.