I put a gallon of colloidal silver in my water tank every day to deal with  a 
bacterial problem.  I don't use the good colloidal silver, made with the  
Silvergen unit.  I fill an empty gallon plastic drinking water jug with tap  
water, put in two .999 pure silver rods each connected to alligator clips with  
the other ends clipped to three 9-volt batteries snapped in a series.   When 
the 
water looks slightly gray-around 5 minutes--it is done.   Cost--maybe 2 cents!
 
Hope this helps,
 
Jill