We have moderately hard water and I use STPP in nearly all loads. I use it in the dishwasher as well. I put 1T in the wash and let it add water for a minute or so to start dissolving, then add detergent.

In the dishwasher I add 1 tbsp to the dispenser along with the detergent.

My silverware shines like new and my clothes are softer.

Where would I find STPP? I am so tired of stiff clothes.

Full name of it is sodium tripolyphosphate.

Search for sellers on Amazon and eBay. There's also chemistrystore.com but their shipping is outrageous. Could be other online sources.

I use this:

https://www.amazon.com/Sodium-Tripolyphosphate-Super-Cleans-Grade/dp/B01JDX5ASQ/ref=sr_1_3?keywords=Sodium+Tripolyphosphate+cesco&qid=1576194408&s=industrial&sr=1-3

@loves2shop: Why don’t you install a water softener?

@dadoes @vinmarks: Is there any benefit to using STPP if you have soft water? I’ve seen it mentioned in the LR a lot, especially by the late, great, laundress herself, @mamapinky (God Rest her soul).

Yes, it's beneficial for boosting the detergent's cleaning power.

Well I guess I’ll have to get some and try it!

There was a surge particularly of people complaining about dishwasher cleaning and residue problems when phosphates were removed from dishwasher detergents, and even buying new machines for lack of finding a solution when their existing/old machine wasn't directly at fault. The complaints largely eased-off as detergent manufacturers tweaked formulas and dishwasher manufacturers modified machine behavior and design to work with them.

I just had our water softener serviced yesterday (they are coming again on Monday to replace the carbon). They tested the water and concluded our softener is doing its job, and then looked for evidence of calcium buildup in the toilet tanks and found none. There is a buildup of residue just inside the door of our DW (which has a stainless steel interior) and they saw spots on the SS kitchen sink. Their verdict is that we use too much soap in the sink, and that the Finish Tablets I use in the DW are too soapy. The one rep (they are husband and wife) recommended I switch to a liquid Cascade product in one cup only. It made me wonder if I am using too much detergent in the laundry seeing how soft our water is. I use 20 Mule Team Borax and Tide for every load. A neighbor who has not yet had a softener installed (an absolute must if you live in San Antonio with its hard limestone infused water) was complaining yesterday about the smell and feel of the water. If your water is so hard you have to add additives, think of what it is doing to your pipes, and your skin. I heartily recommend exploring having a water softener installed.

We had a water softener at our last house and were told to reduce laundry detergent doses to half the amount suggested on the product label. This was for a conventional TL washer.

We were never told to reduce dosing in our DW, so in my naïveté we did not. All our glassware ended up badly etched after several years.

The liquid/gel DW detergents do not have good ratings at CR magazine. Try to find a powder version of Cascade, use half- doses, and see how your dishes fare.

Dishwasher tablets and pods/pacs effectively prevent moderation of the dosage. My untreated TX well water coupled with pacs (Cascade Platinum) causes so much foaming/sudsing that the spray arm rotation and spray force is impaired. A couple loads with these pods are the only time in 16 years that I noticed my dishwasher (which takes only ~0.8 gal per fill) add more water to compensate for the sudsing (it senses the fill level via the electronics monitoring the current draw of the pump motor). There's even a slight foaming in the final rinse although none is evidenced by the time the dry period is over. I normally use Cascade Fryer Boil Out (3 tsp main wash, 1 tsp prewash) which induces no sudsing. I will say the Cascade pacs with enzymes work much better on egg residue (microwaved in a coffee mug) but that's the only advantage I find. A powder detergent with enzymes allows dosage control.

I use the same place to get STTP from as Vinmarks. They are on Ebay. They're cheap and I never had a problem with them.