How do I prevent staining from hard water minerals on the interior surfaces?

To clean hard water mineral film from the interior, apply dishwasher detergent to a damp sponge while wearing rubber gloves. Do not use any type of cleanser other than dishwasher detergent because it may cause foaming or sudsing. Cascade®, Cascade® Complete, and Electrosol® Dishwashing Detergents are approved for this use. (Page 12)