“Here in Tampa they lose roughly 10% of the water to leaks in the pipes. What gets in through those holes?”
Probably nothing, unless there’s a main break, and de-pressurization. The water leaking out is under pressure, and won’t allow anything to leak in.
Sure in theory or a lab. Now throw in random chance, varying water pressure, thousands and thousands of holes of varying types sizes and locations.
Of course there is the chlorine to kill it and the dilution to keep people from getting sick.