The Pink Elephant Lady
The Dish on Spotty Dishes, Rinse Aids, and Hard Water

What is dish washer rinse aid, and why do you need it? Or do you?
Despite its name, rinse aid actually doesn't have anything to do with rinsing your dishes. Instead, it helps remove water from flatware, plates, bowls, and glasses. Really, it's more of a drying aid. Why don't they call it "Dry Aid?" We don't know, but it would have been a lot more accurate.
Rinse aids contain chemicals called surfactants which lower the surface tension of water. So instead of forming droplets, the water spreads into thinner sheets that roll right off your dishes. If you’ve ever used Rain-X on your car’s windshield, you'll have a good idea of what this looks like. Ultimately, this means that your dishes will dry much more quickly.
The other perk is that rinse aid's hydrophobic—or water repellent—properties prevent your dried dishes from showing water spots, which are caused by minerals left behind as water evaporates off a surface. In a perfect world, the water in our pipes would be pure and free of minerals, but in the real world even water that isn’t considered “hard” still contains trace amounts of limestone or chalk.
So, what is 'hard water', anyway?
Hard water is water that has high mineral content (in contrast with "soft water"). Hard water is formed when water percolates through deposits of limestone and chalk which are largely made up of calcium and magnesium carbonates. If your water isn't particularly hard, you might not have as much of an issue with spotty dishes as a friend who has hard water. Hence the fact that I have customers who say, "I have never used a rinse agent and my dishes come out just fine."

Map Source: http://www.haguewater.com/water-problems/hard-water/
The following can all be possible symptoms of hard water:
Strange stains in sinks, showers, and toilets (brown/reddish)
Spotty dishes
Excessive soap scum
Clogged shower heads
Difficulty in making a good lather during handwashing/bathing
Clogged pipes
Difficulty getting laundry truly clean
Skin irritation/aggravation of eczema
Appliances wearing out too soon

Of course, these symptoms are not caused ONLY by hard water, but if a few of them pertain to you, you may have an issue.
Evaluating Rinse Aid Products
The Environmental Working Group grades household products on safety for humans and the environment. Most grocery store brands of rinse aid fail miserably (http://www.ewg.org/guides/subcategories/26-RinseAid).
However, be wary of 'natural' and 'green' websites and blogs telling you to use straight vinegar in your dishwasher’s rinse aid compartment. Yes, it's inexpensive and easy to use. In the long run, however, this might cost you a lot more money than you bargained for! The rinse aid compartments on newer dishwashers have rubber components that aren’t really compatible with the acidity of straight vinegar. Putting vinegar in the dispenser on a regular basis can erode or cause the seal in the dispenser to disintegrate!
Our 'Detoxify the Dish Routine' Bundle
Looking for a safe, green alternative to conventional rinse agents? Pink Elephant Products carries everything you need so your dishes hold only your delicious food - NOT hard water

spots and chemical residues! Automatic dishwasher rinse agent, dish soap for handwashing, and automatic dishwasher powder are part of our Detox the Dish Routine Bundle available on our website. Our bundles contain everything you need to clean each room of your home and for all of your personal care routines:
Laundry Bundle
Body Aches Bundle
Feminine Hygiene Starter Kit for Girls
Fancy Feet Bundle
Pests-be-Gone Bundle
Upholstery and Fabric Bundle
Bundle of Joy
Facial Care Bundles (available for normal, oily, or dry/aging skin)
Hair and Hands Bundle
Clean Cosmetics Bundle
Birthday Bundle for Kids
As always, all products are free of synthetic fragrance and hormone-disrupting chemicals!
SOURCES
What the Heck is Rinse Aid, And Why Do I Need It?
http://dishwashers.reviewed.com/features/what-the-heck-is-rinse-aid-and-why-do-i-need-it
I Tried Eco-Friendly Alternatives to Rinse Aid: Here's What I Found Out http://dishwashers.reviewed.com/features/rinse-aid-alternatives
EWG's Guide to Healthy Cleaning: Rinse Aid
http://www.ewg.org/guides/subcategories/26-RinseAid#.WZ-C4F4s3IU