of hardness removal with that recorded when the ion-exchange resin bed was new, and
calculate the efficiency based on the original capacity as 100 percent. A decrease in
efficiency may be caused by a dirty bed, coated resin grains, loss of ion-exchange bed,
or improper regeneration (either by weak brine solution or under-regeneration or over-
regeneration). Replace resin bed if the efficiency has decreased by 25 percent and it
cannot be almost completely restored by cleaning and using special procedures
recommended by the manufacturer.