[ChildOfThe60s]

This seems to agree with your assessment:

http://ths.gardenweb.com/faq/lists/laundry/2003052601018823.html

That being the case, I wonder how one could purchase the chemical STPP.

[netmilsmom]

I’ll risk the dishwasher and buy what I can find.
Lowes has the TSP for cheap. Now what I need is a “make your own” dishwashing detergent.

All of them on the internet are just Borax and Washing soda. Who knows if that will work.

[Reaganez]

I buy mine at the thechemistrystore.com

http://www.chemistrystore.com/cart.cgi?group=100513&child=100614

I use it in my laundry as well because I have hard water.

If you want to buy “oxyclean” without fillers and perfumes buy sodium precarbonate.

http://www.chemistrystore.com/cart.cgi?group=100513&child=100581

There are also a few DIY soap stores online but never tried them. The Chemistry Store has been very reliable for me and very price competative when shipping is included.