Calgon contained Hexametaphosphate Na6 P6 O18 which is slightly different from Sodium tri polyphosphate Na5 P3 O10 in that a 1% solution of Hexa has a pH of 6.8 while the tripolyphosphate has a pH of 9.7. In the wash, if detergent was used, the phosphate builders like STPP contained in the detergent were used to sequester the calcium and magnesium salts that make water hard. If soap was used for washing, a softener could be needed in the wash to prevent soap curd from forming which was a real problem in automatic washers where the water had to be drained away from the fabrics.
The Norge dispenser wheel added Calgon to the rinse water which is what you are suggesting. Because Norge used an overflow rinse, the Calgon solution, which in the initial dilution helped to liberate the soap or detergent from the fabrics, was rinsed away, neutralized and diluted during the overflow leaving the fabrics soft. My mom used to add a small amount of Calgon to the rinse. When we lived in houses with basements, the foil-wrapped box of Calgon used to get all sticky with the moisture the hygroscopic Calgon would absorb from the humid air down there. If sealable plastic bags had been invented back then, one would have been a good place to store the box of Calgon.
Another good point about adding STPP to the wash water as Glenn suggested was that it enabled you to use less detergent so you generally did not have to add Calgon to the rinse water because as the STPP rinsed out, it facilitated the rinsing out of the smaller amount of detergent. [this post was last edited: 6/22/2024-16:14]