For the most part, well water is safe to drink, but a private well is not regulated by the federal government or most states, so testing it is your job. Bacteria is the one most likely to make you sick, and it has no taste, color or smell. Here is the safe line for each health item on a well test, how often each one turns up in the tests my customers send in, and why boiling kills bacteria but leaves nitrate, arsenic and lead behind.