[Reaganez]

TSP (TriSodiumPhosphate) is NOT the correct additive. It forms a precipitate ... basically dust in the water.
The correct additive is STPP (Sodium TriPolyPhosphate), which does not form a precipitate.

TSP could prematurely wear parts in your dishwasher.

It’s easy to get confused ... STPP ... TSP.

TSP is used in third world countries because of cost not superior results vs STTP.

[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.