Is it okay to add...

[Bill of Osceola]

   Is it Ok to put things like soured milk or yeast into the system?

Will that help, hurt or doesn't matter?

[Toxic Avenger]

Check out the following link.  It should answer your question better than I could here.  The section on page two, entitled Types of Additives and Effects on Treatment Processes, should answer your question.  Sour milk/yeast would be considered a bacterial additive.

http://www.extension.purdue.edu/extmedia/HENV/HENV-13-W.pdf

[Bill of Osceola]

   — Human waste contains abundant bacteria that are
remarkably resilient. There is no need to supplement
the bacteria supply in a septic tank.

This is from the link you gave me.

How do these companies get away with making us think we need additives anyway?

Thank you for saving me some money!! 

[Toxic Avenger]

How do these companies get away with making us think we need additives anyway?

I do think it is a waste of money to buy these products personally, because mostly it is practically impossible for a homeowner to even know if it is helping.  I lot of people out there trust what they hear on TV or read on the labels of products, when the fact is these companies are "marketting" a product so it will sell.  It's not gonna sell if it says, "This product is not necessary for you system, but please buy it anyway."   

[LM Excavating]

How do these companies get away with making us think we need additives anyway?

Everybody needs a way to make money, some choose an honest way and some don't,,,

Hey I read if you put these SPECIAL magnets on your cars fuel line your MPG will increase by 500%!!!

[jmenchhofer]

Check out the following link.  It should answer your question better than I could here.  The section on page two, entitled Types of Additives and Effects on Treatment Processes, should answer your question.  Sour milk/yeast would be considered a bacterial additive.

http://www.extension.purdue.edu/extmedia/HENV/HENV-13-W.pdf

That Purdue fact sheet is my favorite resource for people who ask me if they should use septic system additives.  There are several other similar sources of information out there, but that one is really put together well.  I have yet to see any science-based information that leads me to believe that any septic system additives are necessary, so I recommend against using any of them.