I have a Kenmore water softener (625.388250) that is 7 years old. When
I was adding salt, I notice that the outer shell of the resin tank is
cracked (crack starts about 10 inch from tank bottom). This shell
appears to be a thin covering for the resin tank. My questions a

1) Does this need to be replaced? The part cost is $350 plus shipping
from Sears. At that cost, I would probably buy a new unit.

2) I can buy a similar used water softener (slightly smaller tank but
it should fit) from craigslist. I would swap the two resin tanks. The
softener that is listed has not been used for a few years. Do I need
to be concerned about mold etc in the tank from long term storage?

Thanks.

Philip