One way is for a landowner to gather as much information as possible about his or her private water well, to know how it works, as well as who has had the land before them. The landowner needs to see if anyone has used pesticides in the area, as it can contaminate the well water. This is the most common way. The landowner can also check to see if any other chemicals have been spilt in the area or even a gas or oil leak, as that too can cause the contamination of well water.
I hope this helps.
