To calculate the time if the current and required ppm are known (the normal case).

The formula is: Time (mins) = Volume DW (Ltrs) x ppm Ag x 15 / mA on CC meter

               volume (ltrs) x ppm x 15

time    =     ———————————–

               mA

 
OR
 
To calculate the ppm if the time and current are known:

The formula is:  ppm Ag = Time (mins) x mA on CC meter / Volume DW (Ltrs) x 15

                           time (mins) x mA

ppm Ag     =      —————————–

                          volume DW (Ltrs) x 15