Very true- In my opinion. Those who use well water may introduce bacteria and those who use city water may find their faucets are less sanitary than they imagine- good enough for daily use but liable to introduce bacteria and mold that will thrive and grow in tools and equipment that touch fruit/must/wine which will be kept at close to room temperature for months
Well water contamination depends on where you are. The standard here is a new well needs to be tested and should have an E. coli count of zero per 100ml.
Iron and sulfur metabolizing bacteria are common (use minerals as an energy source) but do not present a health risk. E. coli is the common organism which is used as an indicator of seepage from a fecal source (they grow in human/ animal/ bird intestines). In natural water as streams E. coli will not survive 30 days,,, ie detection says contamination is fresh. Mold would be unusual since drinkable water should not have sugar/ carbon source that mold requires. A lab test for yeast and mold should be zero.
Relative risk; if I am testing
fresh juice an E. coli count of 1 to 10 is not unusual. If I am testing yeast and mold a count of 100 per ml is not unusual, note if it gets above 100,000 you should taste the byproducts. ,,, ie
the must we are fermenting and dirty equipment holds a bigger bacterial and mold risk than well water.
Wine is a preservative system! The food industry knows that the crop comming off the vineyard always has spoilage organisms so we promptly juice the crop, add sulphite, reduce air exposure, add target yeast etc.
If you live near a chemical factory or animal feed lot your risk is higher.
@BernardSmith Know who your neighbor are!