Our water is hard enough to deposit a grey mineral ring at the toilet bowl waterline in a week.   I find that generous use of Tide powder plus ~tbsp STPP functions as fabric softener without the glop of the bottled stuff, waterproof towels, etc.

Definitely does not harm to either clothes or water.

I've never had the precipitate problem with it, and when a glass of our water falls it's an open question what breaks first, the glass or the water.

That said, there's different mineral situations in each location so I don't exclude the possibility.

As to cleaning, I must disagree - it does an outstandingly better job of grease and dirt removal and enzymatic detergents clean far, far better with it than without.

As to STPP, I doubt most people who use it realize how quickly it degrades, so, yeah - most folks using "STPP" unless its fresh aren't.

I still say - try the TSP. If it makes a big difference, invest in STPP. If it doesn't, STPP won't, either.

1) STPP is a much better laundry cleaner than TSP in hard water - it chelates the minerals which interfere with cleaning. No question. That's why I use it.

2) STPP deteriorates quickly if not properly stored - it's on every data sheet, we don't need to pretend it doesn't.

3) If we're now going to pretend TSP doesn't clean and that alkaline conditions are bad for laundry then we might as well just give up.

Nobody is saying STPP isn't wonderful - it is. I use it.

BUT - TSP together with a good enzymatic laundry detergent and hot water cleans really well, especially greasy/oily stains.

Come on folks, are we really going to pretend it doesn't? Are we really going to pretend that one should spend the money on STPP without trying TSP first? That TSP doesn't clean?

Seriously? 

Here's my recipe for dirty clothes:

1/2 cup TSP

145F hot water

1/2 cup Arm&Hammer HE with enzymes

22 minute soak, 14 minute agitation

2 real rinses in a 42 year old Maytag

It never fails.

STPP, 4T instead of 1/2 cup.

We've a couple, I'm using an A702 (the following year it had an extra rinse option, I just reset the dial on this one).

Lovely machine. Never had to do any work on it.

Sometimes I use a '67 Filter-Flo, especially when there's dog hair.

And they come to these conclusions:

1) At 0°C you can store STPP in water and it remains STPP.

2) At 20ºC the disappearance of STPP in water follows first order kinetics.

I'm not posting all the conditions, methodologies, etc. so if you want them, do the research yourself - but:

Worst case (that open cardboard box next to the disgusting garbage pail under the wet, dripping sink) it will have, thanks to the exponential increase in degradation, all turned into something else as fast as I keep saying it will. A few weeks and it's basically TSP.

I stopped posting links when I realized people don't believe two plus two is four when they don't want to, but here's one site where a study may be bought - first page is free. It's enough for those who do actually believe 2 + 2 = 4.

All the other studies I have found come to the same conclusion.

So, yes, if your STPP was always properly stored and you were really cautious with it then you can keep it for quite a while. Just, from everything I've read around here and elsewhere, if you've kept that 5 Kilo bag around for a few years anywhere but in the Arizona dessert - congratulations, you've been using TSP. Not to worry, though - it's a very good cleaner. So good, in fact, until a few decades ago it was the reason we had such clean clothes despite US washers having had such short cycles.

And, yes, since this seems to be vraiment important, TSP doesn't chelate hard water minerals out like STPP does. I love STPP, use it all the time - but dislike people pretending 2+2 doesn't = 4 just 'cause they don't like me.

Sheesh. I'd put any current detergent with the addition of TSP up against one without and guarantee the addition would improve the removal of body oils and cooking/automotive oils noticeably. 

If anybody could store it properly, you are the type who could. The fact that nearly everyone else on the planet does not is the whole reason Automatic Detergent boxes containing the stuff warned not to keep it around too long, the whole reason commercial cleaners with it warn about proper storage.

Come on, you're just being combative out of personal reasons. I've provide the scientific basis for my assertions, it's silly to mix personal feelings with fact. 

STPP has wonderful cleaning abilities, I use it. But - this 'TSP' is of no value as a laundry/dish cleanser is just plain wrong. I've never had the problems with it which are theoretically possible. Water chemistry plays a role in that. So does accepting that STPP doesn't remain STPP for long unless stored with great care.