STPP...Can You Use Too Much?

mieleformeOctober 19, 2010

Thing is I have an unlimited free supply of STPP or as it's labeled Trisodium phosphate. I use it 50/50 with detergent. I never have over sudsing and results are satisfactory. I'm just wondering if I could damage clothing or the machine over time if I happen to use too much. Can an excessive amount have adverse affects on clothing or machine? I don't think I use too much, and everything rinses very well. Truth be told I'm more worried about the machine. Environmentally I'm not concerned, I'm over that. Thanks for the input.

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You've got the wrong stuff.

TriSodium Phosphate = TSP = wrong

STPP = Sodium TriPolyPhosphate = right

While TSP IS a cleaning agent, often used for degreasing, washing driveways, paint-prep and such, STPP is the correct additive for introducing phosphates to laundry & dishwashing.

    Bookmark   October 19, 2010 at 2:27AM
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Chemically what is the difference? I questioned this with a chemist and was told that there was essentially none other than multiple industry names (now I question him). I had actually bought STPP and compared it to TSP by dissolving equal parts in water. Not scientific, I just wanted to feel the effects on the water. Not only do the powders look the same but their effects on the water were the same âÂÂto the touchâÂÂ, both felt like slick soapy water, same smell, and PH was identical. Even a bit of searching I find both described as used in soaps and detergents. DonâÂÂt tell me IâÂÂve been treating my wifeâÂÂs $200 jeans with driveway cleaner.

    Bookmark   October 19, 2010 at 12:08PM
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TriSodium Phosphate Synonyms: Sodium phosphate, tribasic; Sodium orthophosphate; Sodium phosphate; Trisodium orthophosphate; Phosphoric acid, trisodium salt; Sodium phosphate

Sodium TriPolyPhosphate Synonyms: Sodium triphosphate; Triphosphoric acid, pentasodium salt; Sodium Phosphate Tripoly; STPP; pentasodium triphosphate; Pentasodium Tripolyphosphate

    Bookmark   October 19, 2010 at 1:39PM
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Per info in the FAQ here on the Laundry Room Forum, TSP is a simple or "mono" phosphate and generates a precipitate, which is not a good thing for laundry use but not so much a problem washing a driveway. Avoiding precipitates is the reason for using STPP instead of other types of water softeners/boosters.

STPP is a "complex" phosphate compound and does not form a precipitate in the wash water. STPP decomposes into TSP over time with exposure to moisture (detergent packages instruct "store in a cool, dry place" which is to protect the product quality, whether or not phosphates are in it), and thus should be kept in an air-tight container for long-term storage.

    Bookmark   October 19, 2010 at 2:48PM
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Well thanks for the info! IâÂÂm going to dump that crap.

    Bookmark   October 19, 2010 at 4:05PM
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mieleforme, if you had measured the pH of the water after you had dissolved the phosphates you would have found that the TSP is far more basic (alkaline) than STPP. TSP has too much free phosphate too. I use it to dull old paint when I want to repaint a house or interior woodwork.

    Bookmark   October 20, 2010 at 1:32PM
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I have found that if you use too much STPP in your laundry, the rinse water will still have that slimy feeling to it. Your rinse water may be perfectly clear, but it still can have STPP residue in it.

    Bookmark   October 21, 2010 at 11:50AM
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So how much should you use? I've been using about 20ml of STPP per load.

    Bookmark   October 22, 2010 at 11:50AM
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20ml is around how much I use, a tablespoon or sometimes more.

    Bookmark   October 22, 2010 at 8:30PM
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When I was using Persil I used STPP with it and blended 2.5 parts Persil to 1.5 parts STPP. I used a 4 tablespoon dose of that blend on normal wash and double on heavy soiled washes like my work uniforms.

    Bookmark   October 23, 2010 at 9:45AM
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The amount of STPP one uses will be related to how hard your water is. So if you have soft water, 1/2 tsp may be enough.
If you have hard water 2 tbsps may be enough.
The way I judge STPP use is to feel the water. STPP will make the water feel slimy (soft). You want the wash water to be slimy and the rinse water not slimy. STPP will do nothing in the rinse cycle, only in the wash cycle where it helps the detergent get clothes cleaner.

    Bookmark   October 23, 2010 at 12:10PM
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Where do you buy the STPP ?? Can't find it online or at Home Depot.

    Bookmark   November 3, 2010 at 2:20AM
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Yes, it is available online. Probably at several sources. Search by the proper name "sodium tripolyphosphate." One source that's popular is

    Bookmark   November 3, 2010 at 3:20AM
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