Things You'll Need
Dish
Vinegar
Soft cloth
Toothbrush

Hard water stains develop on a number of surfaces, including plastic. When hard water comes into contact with the plastic surface, it dries leaving a cloudy, unattractive film that makes the plastic look unclean. The easiest way to remove the hard water stains is to grab a few items from your cupboard, and begin the stain removal process.
Step 1
Dip the edge of a cleaning cloth into a dish of pure white vinegar. Vinegar will dissolve the marks without damaging the plastic or leaving a residue when dry.
Step 2
Wipe over the hard water stains, using circular buffing motions to get rid of the marks.
Step 3
Dip a toothbrush into the vinegar and scrub hard stains that are not removed with the cloth alone.
Step 4
Soak the plastic overnight in a 50/50 mixture of water and white vinegar for extremely tough stains, if possible.
Step 5
Scrub the plastic with a cloth the following morning, and allow it to air dry.
Mel Frank
Mel Frank is a professional freelance writer with over 15 years of writing experience. She has completed a wide variety of writing assignments for a number of publications that include CNN and various websites. Frank received a Bachelor of Fine Arts from a prestigious university in Pennsylvania.