It is safe for natural rubber seals and any parts made from polypropelene, silicone, fluorocarbon, and virgin Teflon, as well as butyl synthetic rubber seals.
I also know the pH of vinegar. Here is a pH scale for reference:
Distilled white vinegar usually measures between 2.4-3.5 depending on the brand. Now if you look at commercial rinse aids, you will find that many of the brands' key ingredient for getting shiny spot-free dishes is citric acid. Citric acid measures pH 2.2 making it more acetic than vinegar. So how can this claim that vinegar ruins the seals in appliances be true?
My thoughts? I'm glad you asked. Have you purchased a new dishwasher in the past few years? Guess what comes with the new appliance? A complimentary sample bottle of blue rinse aid with a nice postcard advertisement that highly recommends you use this brand of blue rinse aid in their appliance. So that makes me wonder if it's all propaganda? Hmmmm.
So this brings me back to the question: Does Vinegar Damage Rubber Seals? Maybe, but it seems unlikely. If you are unsure of the material of your rubber seals or you don't want to chance it, I recommend the following:
1. Place a small glass right-side up on the top rack of your dishwasher.
2. Fill it with a small amount of distilled white vinegar (1teaspoon to 2 tablespoons depending on the hardness of your water).
3. Run the dishwasher as usual.
This process eliminates the possibility of vinegar sitting on the seals of your rinse aid dispenser.