Liquid soap is usually made from a concentrate that’s diluted with tap water and poured into smaller containers used to refill the soap dispensers. Some cleaning companies may be diluting that concentrate more than recommended to save money, making them less effective against germs.
Gerba found one supplier who was reusing a 30-gallon barrel to mix the soap, and discovered “at the bottom was a half-inch of slime” that no one knew how long had been there.
Commercial soaps contain preservatives designed to inhibit the growth of harmful microbes, but scientists suspect that those preservatives break down over time. And it doesn’t seem to matter whether the soap dispenser is made out of plastic or stainless steel.
I suspect it is not soap but detergent. Water is a perfect medium for bacterial growth. Which is why I avoid any cosmetic products that have water in them that do not contain preservatives. You should see how the “natural” crowd goes bonkers over that issue.
I would never use tap water when making cosmetics for my own use let alone if I ever sold them (I don’t). It would be distilled water. Normal procedure for when water is going to be added is to heat it to a certain temp then hold it at that temp for a specified time. This is in addition to using a preservative. But I get that is not practical for filling those dispensers.
The solution would be to make sure the product is premixed, tested for bacteria before packaging. The dispensers could be lined with a disposable liner which would be changed before each refill. But add tap water over and over again to a dispenser that harbors bacteria already and of course you are gonna get germs in the “soap”. Better yet carry your own soap or other cleanser.