There will be little emphasis on those contaminants tracked through your home from contamination of surface soils. We are primarily concerned about contaminants entering your home through the subsurface. Contaminants that travel through the subsurface and, then enter your home may have been caused by accidental leaks, planned discharges, farming practices, or domestic sources. Often it doesn't take much mass of contamination to expose you or your family to an unacceptable risk. If your potable water is publicly supplied, then any subsurface contaminant exposure is likely limited to that which can enter through your basement wall, crawl space, or slab.
Potable water is supplied either publicly or privately.
The source of potable water is either surface water or ground water that is publicly or privately supplied. Individual public water supply systems can supply millions of people with water of potable quality. It would be coming from a public supply well, which may supply thousands of other people beside you. Potable supplies of public water should not be a concern since it should be appropriately monitored. It just isn't economical to pipe public water into remote rural areas.