Ok ... what an old post, but how did the ebay purchase turn out??
Well, as I said, what you want is STPP, not TSP, anyway.
I did buy STPP on ebay and my clothes are coming out noticeably cleaner and brighter and my dishes are cleaner and sparkle.
Just fine!
The TSP was the real deal. Was in the hardware store the other day and noticed the familiar red and white box - but it’s called something else now.
The STPP is the stuff to get, though. Use it in both the laundry and dishwasher, and it works EXCELLENT. Just about a teaspoon or so in addition to the regular, defanged detergent.
Now, before going out and buying a fifty pound bag, phosphates in this form tends to break down with exposure to air from what I’m reading. Automatic dishwasher detergent often mentions to “use within a few months”; even though phosphates have been removed, the warning still stands. Figures, but that’s why.
I bought a five pound bag of STPP and it lasts a long time. If one could guarantee an absoloutely airtight container it might pay to buy in quantity and transfer to smaller, useable amounts. But it works excellent, particularly noticed glassware that was completely filmed over is now sparkly clear.