I am trying to track down where black sediment is coming from in my drinking water. I have a well , 10 month old conditioner and 10 month old water heater. I have tap the well and no sediment. The folks that make the conditioner have stated that their resin is brown so they are not the one. So, what in the hot water heater could be causing the problem. I have plastic plumbing with coppper flex tube to the water heater.